diff --git a/src/API.php b/src/API.php
index 4e4d3f8..83bdf37 100644
--- a/src/API.php
+++ b/src/API.php
@@ -37,28 +37,24 @@ public function __construct(Client $client)
      */
     public function sendBatch(array $messages)
     {
-        $body = '';
+        $longMessages = [];
+
         /** @var Message\Message $message */
         foreach ($messages as $i => $message) {
             if (!$message instanceof Message\Message) {
                 throw new InvalidArgumentException();
             }
 
-            $body .= "[{$i}]\n";
-            $body .= $message->toINI();
+            $longMessages[] = (new Message\LongMessage)
+                ->setId($i + 1)
+                ->setDstaddr($message->getDstaddr())
+                ->setSmbody($message->getSmbody())
+                ->setDlvtime($message->getDlvtime())
+                ->setVldtime($message->getVldtime())
+                ->setResponse($message->getResponse());
         }
-        $body = trim($body);
-
-        $request = $this->client->newRequest(
-            'POST',
-            $this->client->buildUriWithQuery('/SmSendPost.asp', ['encoding' => 'UTF8']),
-            'text/plain',
-            $body
-        );
 
-        $response = $this->client->sendRequest($request);
-
-        return $this->parseMessageResponse($response);
+        return $this->sendLongMessageBatch($longMessages);
     }
 
     /**
diff --git a/tests/APITest.php b/tests/APITest.php
index 28f294c..2dcbe72 100644
--- a/tests/APITest.php
+++ b/tests/APITest.php
@@ -49,15 +49,8 @@ public function testSendBatch()
                 ->setSmbody('須知反逆得到勝利時 / 社會纔能進步改革'),
         ]);
 
-        $expectedRequestBody = '[0]
-dstaddr=0987654321
-smbody=壓迫孕育反逆 / 反逆產生壓迫
-dlvtime=60
-vldtime=120
-response=https://example.com/callback
-[1]
-dstaddr=0987654322
-smbody=須知反逆得到勝利時 / 社會纔能進步改革';
+        $expectedRequestBody = '1$$0987654321$$60$$120$$$$https://example.com/callback$$壓迫孕育反逆 / 反逆產生壓迫
+2$$0987654322$$$$$$$$$$須知反逆得到勝利時 / 社會纔能進步改革';
 
         $expected = (new Message\Response())
             ->addResult(