diff --git a/serverside_challenge_2/challenge/.gitignore b/serverside_challenge_2/challenge/.gitignore
index 88381219c..9662fde16 100644
--- a/serverside_challenge_2/challenge/.gitignore
+++ b/serverside_challenge_2/challenge/.gitignore
@@ -27,3 +27,9 @@
 
 # Ignore master key for decrypting credentials and more.
 /config/master.key
+
+# Ignore Editor's filepath
+.vscode
+.idea
+
+.tool-versions
\ No newline at end of file
diff --git a/serverside_challenge_2/challenge/README.md b/serverside_challenge_2/challenge/README.md
index 7db80e4ca..09e06eb3d 100644
--- a/serverside_challenge_2/challenge/README.md
+++ b/serverside_challenge_2/challenge/README.md
@@ -1,24 +1,73 @@
-# README
+# 電気料金出力API
+## 概要
+与えられたリクエスト値を元に、一致する電力会社/プランの料金を返却するAPIです。
 
-This README would normally document whatever steps are necessary to get the
-application up and running.
+## API仕様
+### エンドポイント
+```
+GET electricity_charges/calculate
+```
 
-Things you may want to cover:
+### リクエスト値
 
-* Ruby version
+| パラメータ名 | 説明      | データ型 | パラメータ制限                    | 備考      |
+|--------|---------|------|----------------------------|---------|
+| ampere | 契約アンペア数 | int  | 10/15/20/30/40/50/60 のいずれか | 単位: A   |
+| usage  | 電力使用量   | int  | 0以上の整数                     | 単位: kWh |
 
-* System dependencies
+### レスポンス
+| パラメータ名        | 説明    | データ型   | 備考 |
+|---------------|-------|--------|----|
+| provider_name | 電力会社名 | string |    |
+| plan_name     | プラン名  | string |    |
+| price         | 値段    | float  |    |
 
-* Configuration
+### レスポンスのサンプル
+#### 一致するプランがある場合
 
-* Database creation
+```json lines
+// GET http://localhost:3000/electricity_charges/calculate?ampere=30&usage=10
 
-* Database initialization
+[
+  {
+    "provider_name": "東京電力エナジーパートナー",
+    "plan_name": "従量電灯B",
+    "price": 1056.8
+  },
+  {
+    "provider_name": "東京電力エナジーパートナー",
+    "plan_name": "スタンダードS",
+    "price": 1233.25
+  },
+  {
+    "provider_name": "東京ガス",
+    "plan_name": "ずっとも電気1",
+    "price": 1094.7
+  },
+  {
+    "provider_name": "Looopでんき",
+    "plan_name": "おうちプラン",
+    "price": 288.0
+  }
+]
+```
 
-* How to run the test suite
+#### 一致するプランがない場合
 
-* Services (job queues, cache servers, search engines, etc.)
+```json
+[
+  {
+    "message": "ampereに一致するプランが登録されていません"
+  }
+]
+```
 
-* Deployment instructions
 
-* ...
+#### パラメータが不正な場合
+
+```json
+
+{
+  "error": "ampereの値が正しくありません"
+}
+```
\ No newline at end of file
diff --git a/serverside_challenge_2/challenge/app/controllers/electricity_charges/calculate_controller.rb b/serverside_challenge_2/challenge/app/controllers/electricity_charges/calculate_controller.rb
new file mode 100644
index 000000000..8b9294eef
--- /dev/null
+++ b/serverside_challenge_2/challenge/app/controllers/electricity_charges/calculate_controller.rb
@@ -0,0 +1,13 @@
+class ElectricityCharges::CalculateController < ApplicationController
+  include ElectricChargesHelper
+  def calc
+    error, status = validate_params(params)
+    if error
+      return render json: error, status: status
+    end
+
+    calc_result, calc_status = import_price_from_yaml(params[:ampere].to_i, params[:usage].to_i)
+
+    render json: calc_result, status: calc_status
+  end
+end
diff --git a/serverside_challenge_2/challenge/app/helpers/electric_charges_helper.rb b/serverside_challenge_2/challenge/app/helpers/electric_charges_helper.rb
new file mode 100644
index 000000000..66e2abe23
--- /dev/null
+++ b/serverside_challenge_2/challenge/app/helpers/electric_charges_helper.rb
@@ -0,0 +1,74 @@
+module ElectricChargesHelper
+  VALID_CONTRACT_AMPERES = %w(10 15 20 30 40 50 60).freeze
+  VALID_USAGE_REGEX = /\A\d+\z/.freeze
+
+  # リクエストパラメータのバリデーション
+  def validate_params(request_params)
+    # パラメータが不足しているとき
+    if request_params[:ampere].nil? || request_params[:usage].nil?
+      return { error: I18n.t('errors.empty_parameter') }, :bad_request
+    end
+
+    # ampereは特定値である必要がある
+    unless VALID_CONTRACT_AMPERES.include?(request_params[:ampere])
+      return { error: I18n.t('errors.invalid_contract_ampere') }, :bad_request
+    end
+
+    # usageは0以上の整数である必要がある
+    usage = request_params[:usage].to_i
+    unless VALID_USAGE_REGEX.match?(request_params[:usage])
+      return { error: I18n.t('errors.invalid_usage') }, :bad_request
+    end
+    if usage < 0
+      return { error: I18n.t('errors.invalid_usage') }, :bad_request
+    end
+
+    nil
+  end
+
+  # yamlからパラメータ読み込み
+  def import_price_from_yaml(ampere, usage)
+    results = []
+    electricity_charges_data = YAML.load_file("config/electricity_charges.yml")
+    # 基本料金
+    electricity_charges_data["basic_price"].each do |provider|
+      provider["plans"].each do |plan|
+        if plan["amperes"].has_key?(ampere)
+          results << {
+            "provider_name": provider["provider_name"],
+            "plan_name": plan["plan"],
+            "price": plan["amperes"][ampere]
+          }
+        end
+      end
+    end
+
+    # ampereのパラメータに紐づくデータがない場合はその旨を返す
+    if results.empty?
+      results << { message: I18n.t('message.empty_result_by_ampere') }
+      return results, 404
+    end
+
+    # 従量料金
+    results.each do |result|
+      provider_usage_price_data = electricity_charges_data["usage_price"].select{|provider| provider["provider_name"] == result[:provider_name]}
+      provider_usage_price_data.each do |data|
+        plans = data["plans"].select {|plan| plan["plan"] == result[:plan_name]}
+        plans.each do |plan|
+          thresholds = plan["thresholds"]
+          keys = thresholds.keys.map(&:to_i).sort.reverse
+          keys.each do |key|
+            if usage >= key
+              unit_price_kwh = thresholds[key]
+              usage_price = (unit_price_kwh * usage).round(2)
+              result[:price] += usage_price
+              break
+            end
+          end
+        end
+      end
+    end
+
+    [results, 200]
+  end
+end
diff --git a/serverside_challenge_2/challenge/config/electricity_charges.yml b/serverside_challenge_2/challenge/config/electricity_charges.yml
new file mode 100644
index 000000000..40f856395
--- /dev/null
+++ b/serverside_challenge_2/challenge/config/electricity_charges.yml
@@ -0,0 +1,65 @@
+basic_price:
+  - provider_name: 東京電力エナジーパートナー
+    plans:
+      - plan: 従量電灯B
+        amperes:
+          10: 286.00
+          15: 429.00
+          20: 572.00
+          30: 858.00
+          40: 1144.00
+          50: 1430.00
+          60: 1716.00
+      - plan: スタンダードS
+        amperes:
+          10: 311.75
+          15: 467.63
+          20: 623.50
+          30: 935.25
+          40: 1247.00
+          50: 1558.75
+          60: 1870.50
+  - provider_name: 東京ガス
+    plans:
+      - plan: ずっとも電気1
+        amperes:
+          30: 858.00
+          40: 1144.00
+          50: 1430.00
+          60: 1716.00
+  - provider_name: Looopでんき
+    plans:
+      - plan: おうちプラン
+        amperes:
+          10: 0.00
+          15: 0.00
+          20: 0.00
+          30: 0.00
+          40: 0.00
+          50: 0.00
+          60: 0.00
+usage_price:
+  - provider_name: 東京電力エナジーパートナー
+    plans:
+      - plan: 従量電灯B
+        thresholds:
+          0: 19.88
+          121: 26.48
+          301: 30.57
+      - plan: スタンダードS
+        thresholds:
+          0: 29.80
+          121: 36.40
+          301: 40.49
+  - provider_name: 東京ガス
+    plans:
+      - plan: ずっとも電気1
+        thresholds:
+          0: 23.67
+          141: 23.88
+          351: 26.41
+  - provider_name: Looopでんき
+    plans:
+      - plan: おうちプラン
+        thresholds:
+          0: 28.8
\ No newline at end of file
diff --git a/serverside_challenge_2/challenge/config/locales/en.yml b/serverside_challenge_2/challenge/config/locales/ja.yml
similarity index 64%
rename from serverside_challenge_2/challenge/config/locales/en.yml
rename to serverside_challenge_2/challenge/config/locales/ja.yml
index 8ca56fc74..abb35d481 100644
--- a/serverside_challenge_2/challenge/config/locales/en.yml
+++ b/serverside_challenge_2/challenge/config/locales/ja.yml
@@ -30,4 +30,11 @@
 # available at https://guides.rubyonrails.org/i18n.html.
 
 en:
-  hello: "Hello world"
+  errors:
+    empty_parameter: 'リクエストパラメータにampereとusageを設定してください'
+    invalid_parameter_type: 'ampereとusageはいずれも数値を設定してください'
+    invalid_contract_ampere: 'ampereの値が正しくありません'
+    invalid_usage: 'usageは0以上の整数を設定してください'
+  message:
+    empty_result_by_ampere: 'ampereに一致するプランが登録されていません'
+
diff --git a/serverside_challenge_2/challenge/config/routes.rb b/serverside_challenge_2/challenge/config/routes.rb
index 262ffd547..f5caa9839 100644
--- a/serverside_challenge_2/challenge/config/routes.rb
+++ b/serverside_challenge_2/challenge/config/routes.rb
@@ -1,6 +1,5 @@
 Rails.application.routes.draw do
-  # Define your application routes per the DSL in https://guides.rubyonrails.org/routing.html
-
-  # Defines the root path route ("/")
-  # root "articles#index"
+  namespace :electricity_charges do
+    get 'calculate', to: 'calculate#calc'
+  end
 end
diff --git a/serverside_challenge_2/challenge/test/controllers/electricity_charges/calculate_controller_test.rb b/serverside_challenge_2/challenge/test/controllers/electricity_charges/calculate_controller_test.rb
new file mode 100644
index 000000000..72e654be0
--- /dev/null
+++ b/serverside_challenge_2/challenge/test/controllers/electricity_charges/calculate_controller_test.rb
@@ -0,0 +1,80 @@
+require "test_helper"
+
+class ElectricityCharges::CalculateControllerTest < ActionDispatch::IntegrationTest
+  test '正常系: 契約アンペア数 10A, 使用量 0kWh' do
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 286.0  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 311.75 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 0.0 },
+    ]
+    get electricity_charges_calculate_url, params: { ampere: 10, usage: 0 }
+    assert_response :success
+    assert_equal(expected.to_json, response.body)
+  end
+
+  test '正常系: 契約アンペア数 30A, 使用量 100kWh' do
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 2846.0  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 3915.25 },
+      { provider_name: '東京ガス', plan_name: 'ずっとも電気1', price: 3225.0 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 2880.0 },
+    ]
+    get electricity_charges_calculate_url, params: { ampere: 30, usage: 100 }
+    assert_response :success
+    assert_equal(expected.to_json, response.body)
+  end
+
+  test '正常系: 契約アンペア数 60A, 使用量 1000kWh' do
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 32286.0  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 42360.5 },
+      { provider_name: '東京ガス', plan_name: 'ずっとも電気1', price: 28126.0 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 28800.0 },
+    ]
+    get electricity_charges_calculate_url, params: { ampere: 60, usage: 1000 }
+    assert_response :success
+    assert_equal(expected.to_json, response.body)
+  end
+
+  test '異常系: 契約アンペア数 0A' do
+    get electricity_charges_calculate_url, params: { ampere: 0, usage: 100 }
+    assert_response :bad_request
+    assert_equal({ 'error' => 'ampereの値が正しくありません' }.to_json, response.body)
+  end
+
+  test '異常系: 契約アンペア数 70A' do
+    get electricity_charges_calculate_url, params: { ampere: 70, usage: 100 }
+    assert_response :bad_request
+    assert_equal({ 'error' => 'ampereの値が正しくありません' }.to_json, response.body)
+  end
+
+  test '異常系: 使用量 -1kWh' do
+    get electricity_charges_calculate_url, params: { ampere: 30, usage: -1 }
+    assert_response :bad_request
+    assert_equal({ 'error' => 'usageは0以上の整数を設定してください' }.to_json, response.body)
+  end
+
+  test '異常系: 使用量 1.5kWh (型が不正)' do
+    get electricity_charges_calculate_url, params: { ampere: 30, usage: 1.5 }
+    assert_response :bad_request
+    assert_equal({ 'error' => 'usageは0以上の整数を設定してください' }.to_json, response.body)
+  end
+
+  test '異常系: 契約アンペア数 "abc" (型が不正)' do
+    get electricity_charges_calculate_url, params: { ampere: "abc", usage: 100 }
+    assert_response :bad_request
+    assert_equal({ 'error' => 'ampereの値が正しくありません' }.to_json, response.body)
+  end
+
+  test '異常系: 使用量 "abc" (型が不正)' do
+    get electricity_charges_calculate_url, params: { ampere: 30, usage: "abc" }
+    assert_response :bad_request
+    assert_equal({"error"=>"usageは0以上の整数を設定してください"}.to_json, response.body)
+  end
+
+  test '異常系: パラメータが空' do
+    get electricity_charges_calculate_url, params: {}
+    assert_response :bad_request
+    assert_equal({"error"=>"リクエストパラメータにampereとusageを設定してください"}.to_json, response.body)
+  end
+end
diff --git a/serverside_challenge_2/challenge/test/helper/electric_charges_helper_test.rb b/serverside_challenge_2/challenge/test/helper/electric_charges_helper_test.rb
new file mode 100644
index 000000000..d8fc7a6e3
--- /dev/null
+++ b/serverside_challenge_2/challenge/test/helper/electric_charges_helper_test.rb
@@ -0,0 +1,123 @@
+require "test_helper"
+
+class ElectricityChargesHelperTest < ActionDispatch::IntegrationTest
+  include ElectricChargesHelper
+  test '[validate_params]正常系: 契約アンペア数 30A, 使用量 100kWh' do
+    params = { ampere: "30", usage: "100" }
+    assert_nil validate_params(params)
+  end
+
+  test '[validate_params]異常系: 契約アンペア数 0A' do
+    params = { ampere: "0", usage: "100" }
+    error, status = validate_params(params)
+    assert_equal({ error: 'ampereの値が正しくありません' }, error)
+    assert_equal :bad_request, status
+  end
+
+  test '[validate_params]異常系: 使用量 -1kWh' do
+    params = { ampere: "30", usage: "-1" }
+    error, status = validate_params(params)
+    assert_equal({ error: 'usageは0以上の整数を設定してください' }, error)
+    assert_equal :bad_request, status
+  end
+
+  test '[validate_params]異常系: 契約アンペア数 "abc" (型が不正)' do
+    params = { ampere: "abc", usage: "100" }
+    error, status = validate_params(params)
+    assert_equal({ error: 'ampereの値が正しくありません' }, error)
+    assert_equal :bad_request, status
+  end
+
+  test '[validate_params]異常系: 使用量 "abc" (型が不正)' do
+    params = { ampere: "30", usage: "abc" }
+    error, status = validate_params(params)
+    assert_equal({ error: 'usageは0以上の整数を設定してください' }, error)
+    assert_equal :bad_request, status
+  end
+
+  test '[validate_params]異常系: パラメータが空' do
+    params = {}
+    error, status = validate_params(params)
+    assert_equal({ error: 'リクエストパラメータにampereとusageを設定してください' }, error)
+    assert_equal :bad_request, status
+  end
+
+  test '[import_price_from_yaml] 正常系テスト1: 契約アンペア数30A, 使用量100kWh' do
+    result, status = import_price_from_yaml(30, 100)
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 2846.0  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 3915.25 },
+      { provider_name: '東京ガス', plan_name: 'ずっとも電気1', price: 3225.0 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 2880.0 },
+    ]
+    assert_equal expected, result
+    assert_equal 200, status
+  end
+
+  test '[import_price_from_yaml] 正常系テスト2: 契約アンペア数10A, 使用量0kWh' do
+    result, status = import_price_from_yaml(10, 0)
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 286.0  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 311.75 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 0.0 },
+    ]
+    assert_equal expected, result
+    assert_equal 200, status
+  end
+
+  test '[import_price_from_yaml] 正常系テスト3: 契約アンペア数60A, 使用量1000kWh' do
+    result, status = import_price_from_yaml(60, 1000)
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 32286.0  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 42360.5 },
+      { provider_name: '東京ガス', plan_name: 'ずっとも電気1', price: 28126.0 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 28800.0 },
+    ]
+    assert_equal expected, result
+    assert_equal 200, status
+  end
+
+  test '[import_price_from_yaml] 正常系テスト4: 契約アンペア数40A, 使用量200kWh' do
+    result, status = import_price_from_yaml(40, 200)
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 6440.0  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 8527.0 },
+      { provider_name: '東京ガス', plan_name: 'ずっとも電気1', price: 5920.0 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 5760.0 },
+    ]
+    assert_equal expected, result
+    assert_equal 200, status
+  end
+
+  test '[import_price_from_yaml] 異常系テスト: アンペア数に一致するプランがない場合' do
+    result, status = import_price_from_yaml(5, 10)
+    expected = [
+      { message: "ampereに一致するプランが登録されていません"},
+    ]
+    assert_equal expected, result
+    assert_equal 404, status
+  end
+
+  test '[import_price_from_yaml] 境界値テスト1: 契約アンペア数10A, 使用量120kWh' do
+    result, status = import_price_from_yaml(10, 120)
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 2671.6  },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 3887.75 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 3456.0 },
+    ]
+    assert_equal expected, result
+    assert_equal 200, status
+  end
+
+  test '[import_price_from_yaml] 境界値テスト2: 契約アンペア数60A, 使用量351kWh' do
+    result, status = import_price_from_yaml(60, 351)
+    expected = [
+      { provider_name: '東京電力エナジーパートナー', plan_name: '従量電灯B', price: 12446.07 },
+      { provider_name: '東京電力エナジーパートナー', plan_name: 'スタンダードS', price: 16082.49 },
+      { provider_name: '東京ガス', plan_name: 'ずっとも電気1', price: 10985.91 },
+      { provider_name: 'Looopでんき', plan_name: 'おうちプラン', price: 10108.8 },
+    ]
+    assert_equal expected, result
+    assert_equal 200, status
+  end
+end
\ No newline at end of file