diff --git a/app/Exceptions/Handler.php b/app/Exceptions/Handler.php
index dcb27e0..c6fd3a8 100644
--- a/app/Exceptions/Handler.php
+++ b/app/Exceptions/Handler.php
@@ -4,7 +4,10 @@ namespace App\Exceptions;
 
 use Exception;
 use Illuminate\Auth\AuthenticationException;
+use Illuminate\Database\Eloquent\ModelNotFoundException;
 use Illuminate\Foundation\Exceptions\Handler as ExceptionHandler;
+use Illuminate\Http\JsonResponse;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
 class Handler extends ExceptionHandler
 {
@@ -68,4 +71,28 @@ class Handler extends ExceptionHandler
 
         return redirect()->guest(route('login'));
     }
+
+    protected function prepareException(Exception $e)
+    {
+        if (!config('app.debug') && $e instanceof ModelNotFoundException) {
+            return new NotFoundHttpException('Resource not found.', $e);
+        }
+
+        return parent::prepareException($e);
+    }
+
+    protected function prepareJsonResponse($request, Exception $e)
+    {
+        $status = $this->isHttpException($e) ? $e->getStatusCode() : 500;
+
+        return new JsonResponse(
+            [
+                'status' => $status,
+                'error' => $this->convertExceptionToArray($e),
+            ],
+            $status,
+            $this->isHttpException($e) ? $e->getHeaders() : [],
+            JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES
+        );
+    }
 }
diff --git a/app/Http/Kernel.php b/app/Http/Kernel.php
index 1804b56..927364c 100644
--- a/app/Http/Kernel.php
+++ b/app/Http/Kernel.php
@@ -40,6 +40,7 @@ class Kernel extends HttpKernel
 
         'api' => [
             'throttle:60,1',
+            \App\Http\Middleware\EnforceJson::class,
             \Illuminate\Routing\Middleware\SubstituteBindings::class,
         ],
 
diff --git a/app/Http/Middleware/EnforceJson.php b/app/Http/Middleware/EnforceJson.php
new file mode 100644
index 0000000..c139bae
--- /dev/null
+++ b/app/Http/Middleware/EnforceJson.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+
+/**
+ * Request headerに Accept: application/json を上書きする。APIエンドポイント用。
+ */
+class EnforceJson
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @param  \Closure  $next
+     * @return mixed
+     */
+    public function handle($request, Closure $next)
+    {
+        $request->headers->set('Accept', 'application/json');
+
+        return $next($request);
+    }
+}