diff --git a/src/main/java/com/indayvidual/server/domain/todo/controller/TodoCategoryController.java b/src/main/java/com/indayvidual/server/domain/todo/controller/TodoCategoryController.java
index e10d659..a708575 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/controller/TodoCategoryController.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/controller/TodoCategoryController.java
@@ -45,4 +45,17 @@ public ApiResponse<List<CategoryResponseDTO>> getCategories() {
                 SuccessStatus.GET_CATEGORIES_SUCCESS.getCode(),
                 SuccessStatus.GET_CATEGORIES_SUCCESS.getMessage());
     }
+
+    @Operation(summary = "카테고리 삭제", description = """
+            카테고리를 삭제합니다.\n
+            **카테고리 내 할 일도 모두 삭제됩니다.**""")
+    @DeleteMapping("/{categoryId}")
+    public ApiResponse<Void> deleteCategory(@PathVariable Long categoryId) {
+        Long userId = Utils.getUserId();
+        categoryCommandService.delete(userId, categoryId);
+        return ApiResponse.onSuccess(
+                null,
+                SuccessStatus.DELETE_CATEGORY_SUCCESS.getCode(),
+                SuccessStatus.DELETE_CATEGORY_SUCCESS.getMessage());
+    }
 }
diff --git a/src/main/java/com/indayvidual/server/domain/todo/controller/TodoTaskController.java b/src/main/java/com/indayvidual/server/domain/todo/controller/TodoTaskController.java
index ad70f4c..177db3c 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/controller/TodoTaskController.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/controller/TodoTaskController.java
@@ -2,6 +2,7 @@
 
 import com.indayvidual.server.domain.todo.dto.request.*;
 import com.indayvidual.server.domain.todo.dto.response.TaskCheckUpdateResponseDTO;
+import com.indayvidual.server.domain.todo.dto.response.TaskOrderCategoryUpdateResponseDTO;
 import com.indayvidual.server.domain.todo.dto.response.TaskResponseDTO;
 import com.indayvidual.server.domain.todo.dto.response.TaskUpdateResponseDTO;
 import com.indayvidual.server.domain.todo.service.task.TaskCommandService;
@@ -110,22 +111,18 @@ public ApiResponse<TaskCheckUpdateResponseDTO> updateTaskStatus(@PathVariable Lo
                 SuccessStatus.UPDATE_TASK_CHECK_SUCCESS.getMessage());
     }
 
-    @Operation(summary = "할 일 순서 변경",
+    @Operation(summary = "할 일 순서 및 카테고리 변경",
             description = """
-                    카테고리 내 할 일의 순서를 변경합니다.\n
-                    **해당 카테고리 내 모든 Task ID**를 정렬 순서대로 request body로 전달해야 합니다.\n  
-                    해당 순서를 기준으로 `position` 필드를 재정렬합니다.
+                    할 일의 순서 또는 카테고리를 변경합니다.\n
+                    순서/카테고리가 변경되는 모든 `task`의 정보를 포함해야 합니다.
                     """)
-    @PatchMapping("/categories/{categoryId}/tasks/order")
-    public ApiResponse<Void> updateTaskOrder(
-            @PathVariable Long categoryId,
-            @RequestBody @Valid TaskOrderUpdateRequestDTO request) {
+    @PatchMapping("/tasks/order")
+    public ApiResponse<TaskOrderCategoryUpdateResponseDTO> updateTaskOrder(
+            @RequestBody @Valid TaskOrderCategoryUpdateBulkRequestDTO request) {
 
-        //TODO : 카테고리 변경도 추가하기
         Long userId = Utils.getUserId();
-        taskCommandService.updateTaskOrder(userId, categoryId, request);
         return ApiResponse.onSuccess(
-                null,
+                taskCommandService.updateTaskOrders(userId, request),
                 SuccessStatus.UPDATE_TASK_ORDER_SUCCESS.getCode(),
                 SuccessStatus.UPDATE_TASK_ORDER_SUCCESS.getMessage());
     }
diff --git a/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderCategoryUpdateBulkRequestDTO.java b/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderCategoryUpdateBulkRequestDTO.java
new file mode 100644
index 0000000..ce04d24
--- /dev/null
+++ b/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderCategoryUpdateBulkRequestDTO.java
@@ -0,0 +1,13 @@
+package com.indayvidual.server.domain.todo.dto.request;
+
+import jakarta.validation.constraints.NotEmpty;
+import lombok.Data;
+
+import java.util.List;
+
+@Data
+public class TaskOrderCategoryUpdateBulkRequestDTO {
+
+    @NotEmpty(message = "tasks 리스트는 비어 있을 수 없습니다.")
+    private List<TaskOrderCategoryUpdateRequestDTO> tasks;
+}
diff --git a/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderCategoryUpdateRequestDTO.java b/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderCategoryUpdateRequestDTO.java
new file mode 100644
index 0000000..571c309
--- /dev/null
+++ b/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderCategoryUpdateRequestDTO.java
@@ -0,0 +1,19 @@
+package com.indayvidual.server.domain.todo.dto.request;
+
+import jakarta.validation.constraints.Min;
+import jakarta.validation.constraints.NotNull;
+import lombok.Data;
+
+@Data
+public class TaskOrderCategoryUpdateRequestDTO {
+
+    @NotNull(message = "taskId는 필수입니다.")
+    private Long taskId;
+
+    @NotNull(message = "categoryId는 필수입니다.")
+    private Long categoryId;
+
+    @NotNull(message = "order는 필수입니다.")
+    @Min(value = 0, message = "order는 0 이상이어야 합니다.")
+    private Integer order;
+}
\ No newline at end of file
diff --git a/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderUpdateRequestDTO.java b/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderUpdateRequestDTO.java
deleted file mode 100644
index f825409..0000000
--- a/src/main/java/com/indayvidual/server/domain/todo/dto/request/TaskOrderUpdateRequestDTO.java
+++ /dev/null
@@ -1,13 +0,0 @@
-package com.indayvidual.server.domain.todo.dto.request;
-
-import jakarta.validation.constraints.NotEmpty;
-import lombok.Data;
-
-import java.util.List;
-
-@Data
-public class TaskOrderUpdateRequestDTO {
-
-    @NotEmpty(message = "taskOrder 리스트는 비어 있을 수 없습니다.")
-    private List<Long> taskOrder;
-}
diff --git a/src/main/java/com/indayvidual/server/domain/todo/dto/response/TaskOrderCategoryUpdateResponseDTO.java b/src/main/java/com/indayvidual/server/domain/todo/dto/response/TaskOrderCategoryUpdateResponseDTO.java
new file mode 100644
index 0000000..e30e2aa
--- /dev/null
+++ b/src/main/java/com/indayvidual/server/domain/todo/dto/response/TaskOrderCategoryUpdateResponseDTO.java
@@ -0,0 +1,19 @@
+package com.indayvidual.server.domain.todo.dto.response;
+
+import lombok.Builder;
+import lombok.Getter;
+
+import java.util.List;
+
+@Getter
+@Builder
+public class TaskOrderCategoryUpdateResponseDTO {
+
+    private Integer updatedCount;
+    private List<Long> affectedCategories;
+
+    public TaskOrderCategoryUpdateResponseDTO(int updatedCount, List<Long> affectedCategories) {
+        this.updatedCount = updatedCount;
+        this.affectedCategories = affectedCategories;
+    }
+}
diff --git a/src/main/java/com/indayvidual/server/domain/todo/entity/Task.java b/src/main/java/com/indayvidual/server/domain/todo/entity/Task.java
index f359a38..86fbdef 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/entity/Task.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/entity/Task.java
@@ -74,6 +74,11 @@ public void updatePosition(int position) {
         this.position = position;
     }
 
+    public void updateCategory(Category category) {
+        log.debug("[TASK] 카테고리 변경 - before: {}, after: {}", this.category, category);
+        this.category = category;
+    }
+
     public static Task create(User user, Category category, String title, LocalDate dueDate, int position) {
         return Task.builder()
                 .user(user)
diff --git a/src/main/java/com/indayvidual/server/domain/todo/repository/CategoryRepository.java b/src/main/java/com/indayvidual/server/domain/todo/repository/CategoryRepository.java
index 2ae9889..0ed93d4 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/repository/CategoryRepository.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/repository/CategoryRepository.java
@@ -4,8 +4,13 @@
 import org.springframework.data.jpa.repository.JpaRepository;
 
 import java.util.List;
+import java.util.Optional;
 
 public interface CategoryRepository extends JpaRepository<Category, Long> {
 
     List<Category> findAllByUserIdOrderByCreatedAtDesc(Long userId);
+
+    Optional<Category> findByIdAndUserId(Long userId, Long categoryId);
+
+    boolean existsByIdAndUserId(Long categoryId, Long userId);
 }
diff --git a/src/main/java/com/indayvidual/server/domain/todo/repository/TaskRepository.java b/src/main/java/com/indayvidual/server/domain/todo/repository/TaskRepository.java
index c14c0b1..7989cb4 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/repository/TaskRepository.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/repository/TaskRepository.java
@@ -29,4 +29,8 @@ public interface TaskRepository extends JpaRepository<Task, Long> {
      */
     @Query("SELECT MAX(t.position) FROM Task t WHERE t.category.id = :categoryId")
     Integer findMaxPositionByCategoryId(@Param("categoryId") Long categoryId);
+
+    List<Task> findAllByUserIdAndCategoryId(Long userId, Long categoryId);
+
+    List<Task> findAllByCategoryId(Long categoryId);
 }
diff --git a/src/main/java/com/indayvidual/server/domain/todo/service/category/CategoryCommandService.java b/src/main/java/com/indayvidual/server/domain/todo/service/category/CategoryCommandService.java
index 1e0aaab..a7195b2 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/service/category/CategoryCommandService.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/service/category/CategoryCommandService.java
@@ -4,20 +4,27 @@
 import com.indayvidual.server.domain.todo.dto.request.CategoryCreateRequestDTO;
 import com.indayvidual.server.domain.todo.dto.response.CategoryResponseDTO;
 import com.indayvidual.server.domain.todo.entity.Category;
+import com.indayvidual.server.domain.todo.entity.Task;
 import com.indayvidual.server.domain.todo.repository.CategoryRepository;
+import com.indayvidual.server.domain.todo.repository.TaskRepository;
 import com.indayvidual.server.domain.user.entity.User;
 import com.indayvidual.server.domain.user.repository.UserRepository;
 import com.indayvidual.server.global.api.code.status.ErrorStatus;
 import com.indayvidual.server.global.exception.GeneralException;
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.List;
+
 @Service
+@Slf4j
 @RequiredArgsConstructor
 public class CategoryCommandService {
 
     private final CategoryRepository categoryRepository;
+    private final TaskRepository taskRepository;
     private final CategoryConverter categoryConverter;
     private final UserRepository userRepository;
 
@@ -31,4 +38,18 @@ public CategoryResponseDTO create(CategoryCreateRequestDTO request, Long userId)
         Category saved = categoryRepository.save(entity);
         return categoryConverter.toResponse(saved);
     }
+
+    @Transactional
+    public void delete(Long userId, Long categoryId) {
+        Category category = categoryRepository.findByIdAndUserId(categoryId, userId)
+                .orElseThrow(() -> new GeneralException(ErrorStatus.TASK_CATEGORY_NOT_FOUND));
+
+        // 연관된 task 먼저 삭제
+        List<Task> tasks = taskRepository.findAllByCategoryId(categoryId);
+        taskRepository.deleteAll(tasks);
+
+        categoryRepository.delete(category);
+
+        log.debug("[CATEGORY] 삭제 완료 - categoryId={}", categoryId);
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandService.java b/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandService.java
index b5e24c5..6e0fdc7 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandService.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandService.java
@@ -2,9 +2,10 @@
 
 import com.indayvidual.server.domain.todo.dto.request.TaskCreateRequestDTO;
 import com.indayvidual.server.domain.todo.dto.request.TaskDueDateUpdateRequestDTO;
-import com.indayvidual.server.domain.todo.dto.request.TaskOrderUpdateRequestDTO;
+import com.indayvidual.server.domain.todo.dto.request.TaskOrderCategoryUpdateBulkRequestDTO;
 import com.indayvidual.server.domain.todo.dto.request.TaskTitleUpdateRequestDTO;
 import com.indayvidual.server.domain.todo.dto.response.TaskCheckUpdateResponseDTO;
+import com.indayvidual.server.domain.todo.dto.response.TaskOrderCategoryUpdateResponseDTO;
 import com.indayvidual.server.domain.todo.dto.response.TaskResponseDTO;
 import com.indayvidual.server.domain.todo.dto.response.TaskUpdateResponseDTO;
 
@@ -44,10 +45,9 @@ public interface TaskCommandService {
      * 특정 카테고리 내 할 일의 순서를 일괄 변경합니다.
      *
      * @param userId
-     * @param categoryId
      * @param request    요청 DTO
      */
-    void updateTaskOrder(Long userId, Long categoryId, TaskOrderUpdateRequestDTO request);
+    TaskOrderCategoryUpdateResponseDTO updateTaskOrders(Long userId, TaskOrderCategoryUpdateBulkRequestDTO request);
 
     /**
      * 할 일의 체크 상태를 토글합니다.
diff --git a/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandServiceImpl.java b/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandServiceImpl.java
index af2606b..f197ac4 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandServiceImpl.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskCommandServiceImpl.java
@@ -1,11 +1,9 @@
 package com.indayvidual.server.domain.todo.service.task;
 
 import com.indayvidual.server.domain.todo.converter.TaskConverter;
-import com.indayvidual.server.domain.todo.dto.request.TaskCreateRequestDTO;
-import com.indayvidual.server.domain.todo.dto.request.TaskDueDateUpdateRequestDTO;
-import com.indayvidual.server.domain.todo.dto.request.TaskOrderUpdateRequestDTO;
-import com.indayvidual.server.domain.todo.dto.request.TaskTitleUpdateRequestDTO;
+import com.indayvidual.server.domain.todo.dto.request.*;
 import com.indayvidual.server.domain.todo.dto.response.TaskCheckUpdateResponseDTO;
+import com.indayvidual.server.domain.todo.dto.response.TaskOrderCategoryUpdateResponseDTO;
 import com.indayvidual.server.domain.todo.dto.response.TaskResponseDTO;
 import com.indayvidual.server.domain.todo.dto.response.TaskUpdateResponseDTO;
 import com.indayvidual.server.domain.todo.entity.Category;
@@ -21,8 +19,7 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.stream.Collectors;
 
 @Service
@@ -127,67 +124,159 @@ public TaskCheckUpdateResponseDTO toggleCheck(Long userId, Long taskId) {
      * 카테고리 내 할 일 순서를 변경합니다.
      */
     @Transactional
-    public void updateTaskOrder(Long userId, Long categoryId, TaskOrderUpdateRequestDTO request) {
-        List<Long> taskIds = validateTaskOrderRequest(request);
-        List<Task> tasks = findAndValidateTasks(userId, categoryId, taskIds);
-        applyTaskPositionChanges(tasks, taskIds);
+    public TaskOrderCategoryUpdateResponseDTO updateTaskOrders(Long userId, TaskOrderCategoryUpdateBulkRequestDTO request) {
+        // 요청 유효성 검사
+        List<TaskOrderCategoryUpdateRequestDTO> taskRequests = validateTaskOrdersRequest(request);
 
-        log.debug("[TASK] 순서 변경 완료 - categoryId={}, userId={}, taskCount={}",
-                categoryId, userId, taskIds.size());
+        // 유효성 검사
+        Map<Long, Task> taskMap = loadAndValidateTasks(userId, taskRequests);
+
+        // 카테고리 별 재정렬
+        Set<Long> affectedCategories = applyCategoryWiseReordering(userId, taskRequests, taskMap);
+
+        log.debug("[TASK] 순서 변경 완료 - affectedCategories={}, userId={}, taskCount={}",
+                affectedCategories, userId, taskRequests.size());
+
+        // DTO 생성
+        return buildReorderResponse(taskRequests.size(), affectedCategories);
     }
 
     /**
-     * Task 순서 변경 요청의 유효성을 검증합니다.
+     * 응답 DTO를 생성합니다.
+     *
+     * @param size
+     * @param affectedCategories
+     * @return
      */
-    private List<Long> validateTaskOrderRequest(TaskOrderUpdateRequestDTO request) {
-        List<Long> taskIds = request.getTaskOrder();
-        if (taskIds == null || taskIds.isEmpty()) {
-            log.warn("[TASK] 빈 taskOrder 요청");
-            throw new GeneralException(ErrorStatus.TASK_INVALID_ORDER);
+    private TaskOrderCategoryUpdateResponseDTO buildReorderResponse(int size, Set<Long> affectedCategories) {
+        return new TaskOrderCategoryUpdateResponseDTO(size, new ArrayList<>(affectedCategories));
+    }
+
+    /**
+     * 할 일의 순서 변경 또는 카테고리를 변경합니다.
+     *
+     * @param userId
+     * @param requestList
+     * @param taskMap
+     * @return
+     */
+    private Set<Long> applyCategoryWiseReordering(
+            Long userId,
+            List<TaskOrderCategoryUpdateRequestDTO> requestList,
+            Map<Long, Task> taskMap
+    ) {
+        Set<Long> affectedCategories = new HashSet<>();
+
+        // 1. 요청을 카테고리별로 groupBy
+        Map<Long, List<TaskOrderCategoryUpdateRequestDTO>> groupedRequests =
+                requestList.stream().collect(Collectors.groupingBy(TaskOrderCategoryUpdateRequestDTO::getCategoryId));
+
+        for (Map.Entry<Long, List<TaskOrderCategoryUpdateRequestDTO>> entry : groupedRequests.entrySet()) {
+            Long categoryId = entry.getKey();
+            List<TaskOrderCategoryUpdateRequestDTO> requestTasks = entry.getValue();
+
+            Category category = categoryRepository.findById(categoryId)
+                    .orElseThrow(() -> new GeneralException(ErrorStatus.TASK_CATEGORY_NOT_FOUND));
+
+            log.debug("[TASK][REORDER] categoryId={} - 요청된 task 수: {}", categoryId, requestTasks.size());
+
+            // 2. 해당 카테고리의 전체 task 조회
+            List<Task> allTasksInCategory = taskRepository.findAllByUserIdAndCategoryId(userId, categoryId);
+            log.debug("[TASK][REORDER] categoryId={} - DB 내 전체 task 수: {}", categoryId, allTasksInCategory.size());
+
+            // 3. 요청된 task 정렬용 Map
+            Map<Long, Integer> requestedOrderMap = requestTasks.stream()
+                    .collect(Collectors.toMap(TaskOrderCategoryUpdateRequestDTO::getTaskId, TaskOrderCategoryUpdateRequestDTO::getOrder));
+
+            // 4. 요청된 task 정렬
+            List<Task> requestedTasks = requestTasks.stream()
+                    .map(dto -> taskMap.get(dto.getTaskId()))
+                    .sorted(Comparator.comparingInt(task -> requestedOrderMap.get(task.getId())))
+                    .toList();
+
+            log.debug("[TASK][REORDER] 요청된 task 순서:");
+            for (int i = 0; i < requestedTasks.size(); i++) {
+                Task t = requestedTasks.get(i);
+                log.debug("  - [{}] taskId={}, 요청 order={}", i, t.getId(), requestedOrderMap.get(t.getId()));
+            }
+
+            // 5. 요청되지 않은 task
+            Set<Long> requestedIds = new HashSet<>(requestedOrderMap.keySet());
+            List<Task> untouchedTasks = allTasksInCategory.stream()
+                    .filter(task -> !requestedIds.contains(task.getId()))
+                    .toList();
+
+            log.debug("[TASK][REORDER] 포함되지 않은 task 수: {}", untouchedTasks.size());
+
+            // 6. 최종 정렬 리스트 구성
+            List<Task> finalSortedTasks = new ArrayList<>();
+            finalSortedTasks.addAll(requestedTasks);
+            finalSortedTasks.addAll(untouchedTasks);
+
+            log.debug("[TASK][REORDER] 최종 정렬 후 position 재할당:");
+
+            for (int i = 0; i < finalSortedTasks.size(); i++) {
+                Task task = finalSortedTasks.get(i);
+
+                // 카테고리 변경 필요 시
+                if (!task.getCategory().getId().equals(categoryId)) {
+                    log.debug("  - taskId={} 카테고리 변경: {} → {}", task.getId(), task.getCategory().getId(), categoryId);
+                    task.updateCategory(category);
+                }
+
+                // position 재할당
+                log.debug("  - taskId={}, 기존 position={}, 신규 position={}", task.getId(), task.getPosition(), i);
+                task.updatePosition(i);
+            }
+
+            affectedCategories.add(categoryId);
         }
-        return taskIds;
+
+        log.debug("[TASK][REORDER] 전체 변경 완료 - userId={}, 변경된 카테고리 수: {}", userId, affectedCategories.size());
+        return affectedCategories;
     }
 
     /**
-     * Task를 조회, 검증합니다.
+     * Task가 유효한지 확인합니다.
      *
      * @param userId
-     * @param categoryId
-     * @param taskIds
-     * @return Task list
+     * @param taskRequests
+     * @return
      */
-    private List<Task> findAndValidateTasks(Long userId, Long categoryId, List<Long> taskIds) {
+    private Map<Long, Task> loadAndValidateTasks(
+            Long userId,
+            List<TaskOrderCategoryUpdateRequestDTO> taskRequests
+    ) {
+        // task id 추출
+        List<Long> taskIds = taskRequests.stream().map(TaskOrderCategoryUpdateRequestDTO::getTaskId).toList();
+
         List<Task> tasks = taskRepository.findAllById(taskIds);
+
+        // 요청 taskId 개수와 조회한 결과 개수가 다른 경우 예외 처리
         if (tasks.size() != taskIds.size()) {
-            log.warn("[TASK] 일부 taskId 존재하지 않음");
             throw new GeneralException(ErrorStatus.TASK_NOT_FOUND);
         }
 
         for (Task task : tasks) {
-            if (!task.getCategory().getId().equals(categoryId) || !task.getUser().getId().equals(userId)) {
-                log.warn("[TASK] 잘못된 소속의 task 존재 - taskId={}", task.getId());
+            // task.userId와 요청한 userId가 다른 경우 예외 처리
+            if (!task.getUser().getId().equals(userId)) {
                 throw new GeneralException(ErrorStatus.TASK_FORBIDDEN);
             }
         }
 
-        return tasks;
+        return tasks.stream().collect(Collectors.toMap(Task::getId, t -> t));
     }
 
     /**
-     * Task에 순서를 적용합니다.
-     *
-     * @param tasks
-     * @param orderedIds
+     * Task 순서 변경 요청의 유효성을 검증합니다.
      */
-    private void applyTaskPositionChanges(List<Task> tasks, List<Long> orderedIds) {
-        Map<Long, Task> taskMap = tasks.stream()
-                .collect(Collectors.toMap(Task::getId, t -> t));
-
-        for (int i = 0; i < orderedIds.size(); i++) {
-            Long taskId = orderedIds.get(i);
-            Task task = taskMap.get(taskId);
-            task.updatePosition(i);
+    private List<TaskOrderCategoryUpdateRequestDTO> validateTaskOrdersRequest(TaskOrderCategoryUpdateBulkRequestDTO request) {
+        List<TaskOrderCategoryUpdateRequestDTO> tasks = request.getTasks();
+        if (tasks == null || tasks.isEmpty()) {
+            log.warn("[TASK] 빈 taskOrder 요청");
+            throw new GeneralException(ErrorStatus.TASK_INVALID_ORDER);
         }
+        return tasks;
     }
 
     private Task findTaskByIdAndUserId(Long taskId, Long userId) {
diff --git a/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskQueryServiceImpl.java b/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskQueryServiceImpl.java
index 8527f7c..6a6f42b 100644
--- a/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskQueryServiceImpl.java
+++ b/src/main/java/com/indayvidual/server/domain/todo/service/task/TaskQueryServiceImpl.java
@@ -3,7 +3,10 @@
 import com.indayvidual.server.domain.todo.converter.TaskConverter;
 import com.indayvidual.server.domain.todo.dto.response.TaskResponseDTO;
 import com.indayvidual.server.domain.todo.entity.Task;
+import com.indayvidual.server.domain.todo.repository.CategoryRepository;
 import com.indayvidual.server.domain.todo.repository.TaskRepository;
+import com.indayvidual.server.global.api.code.status.ErrorStatus;
+import com.indayvidual.server.global.exception.GeneralException;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
@@ -18,6 +21,7 @@
 public class TaskQueryServiceImpl implements TaskQueryService {
 
     private final TaskRepository taskRepository;
+    private final CategoryRepository categoryRepository;
     private final TaskConverter taskConverter;
 
     @Override
@@ -25,6 +29,12 @@ public class TaskQueryServiceImpl implements TaskQueryService {
     public List<TaskResponseDTO> findTasksByCategoryAndDate(Long userId, Long categoryId, LocalDate dueDate) {
         log.debug("[TASK-QUERY] 할 일 조회 요청 - userId={}, categoryId={}, date={}", userId, categoryId, dueDate);
 
+        boolean categoryExists = categoryRepository.existsByIdAndUserId(categoryId, userId);
+        if (!categoryExists) {
+            log.warn("[TASK-QUERY] 존재하지 않는 카테고리 - categoryId={}, userId={}", categoryId, userId);
+            throw new GeneralException(ErrorStatus.TASK_CATEGORY_NOT_FOUND);
+        }
+
         List<Task> tasks = taskRepository.findByUserIdAndCategoryIdAndDueDate(userId, categoryId, dueDate);
 
         log.debug("[TASK-QUERY] 조회된 할 일 수: {}", tasks.size());
diff --git a/src/main/java/com/indayvidual/server/global/api/code/status/SuccessStatus.java b/src/main/java/com/indayvidual/server/global/api/code/status/SuccessStatus.java
index 6f69e8b..40c3e70 100644
--- a/src/main/java/com/indayvidual/server/global/api/code/status/SuccessStatus.java
+++ b/src/main/java/com/indayvidual/server/global/api/code/status/SuccessStatus.java
@@ -32,13 +32,14 @@ public enum SuccessStatus implements BaseCode {
     // 할 일 관련 응답
     CREATE_CATEGORY_SUCCESS(HttpStatus.CREATED, "CREATE_CATEGORY_SUCCESS", "카테고리 등록 성공"),
     GET_CATEGORIES_SUCCESS(HttpStatus.OK, "GET_CATEGORIES_SUCCESS", "카테고리 목록 조회 성공"),
+    DELETE_CATEGORY_SUCCESS(HttpStatus.OK, "DELETE_CATEGORY_SUCCESS", "카테고리 삭제 성공"),
     CREATE_TASK_SUCCESS(HttpStatus.CREATED, "CREATE_TASK_SUCCESS", "할일 등록 성공"),
     GET_TASKS_SUCCESS(HttpStatus.OK, "GET_TASKS_SUCCESS", "할일 목록 조회 성공"),
     UPDATE_TASK_TITLE_SUCCESS(HttpStatus.OK, "UPDATE_TASK_TITLE_SUCCESS", "할일 제목 수정 성공"),
     UPDATE_TASK_DUE_DATE_SUCCESS(HttpStatus.OK, "UPDATE_TASK_DUEDATE_SUCCESS", "할일 날짜 수정 성공"),
     DELETE_TASK_SUCCESS(HttpStatus.OK, "DELETE_TASK_SUCCESS", "할일 삭제 성공"),
     UPDATE_TASK_CHECK_SUCCESS(HttpStatus.OK, "UPDATE_TASK_CHECK_SUCCESS", "할일 체크 상태 변경 성공"),
-    UPDATE_TASK_ORDER_SUCCESS(HttpStatus.OK, "UPDATE_TASK_ORDER_SUCCESS", "할일 순서 변경 성공"),
+    UPDATE_TASK_ORDER_SUCCESS(HttpStatus.OK, "UPDATE_TASK_ORDER_SUCCESS", "할일 순서 및 카테고리 이동 성공"),
 
     // 색상 관련 응답
     GET_COLORS_SUCCESS(HttpStatus.OK, "GET_COLORS_SUCCESS", "색상 목록 조회 성공")