diff --git a/backend/app/Http/Controllers/Api/AuthenticationTrait.php b/backend/app/Http/Controllers/Api/AuthenticationTrait.php
index ab312b68..3c306b26 100644
--- a/backend/app/Http/Controllers/Api/AuthenticationTrait.php
+++ b/backend/app/Http/Controllers/Api/AuthenticationTrait.php
@@ -36,7 +36,7 @@ trait AuthenticationTrait {
 
         $validate = Validator::make($r->all(), [
             $chk[0] => 'required|'.$chk[2],
-            'password' => 'required|min:8|max:72|alpha_num',
+            'password' => ['required', 'min:8', 'max:72', new \App\Rules\Hankaku],
         ]);
 
         // バリデーションエラー
diff --git a/backend/app/Http/Controllers/Api/ChildrenController.php b/backend/app/Http/Controllers/Api/ChildrenController.php
index ce6af06d..10b693e3 100644
--- a/backend/app/Http/Controllers/Api/ChildrenController.php
+++ b/backend/app/Http/Controllers/Api/ChildrenController.php
@@ -126,7 +126,7 @@ class ChildrenController extends Controller {
         $validate = Validator::make($r->all(), [
             'identity' => 'required|max:20|alpha_num',
             'email' => 'required|unique:children|max:255|email',
-            'password' => 'required|min:8|max:72|confirmed|alpha_num',
+            'password' => ['required', 'min:8', 'max:72', 'confirmed', new \App\Rules\Hankaku],
             'last_name' => 'required|max:100',
             'first_name' => 'required|max:100',
             'image' => 'image_size|image_meme',
@@ -529,7 +529,7 @@ class ChildrenController extends Controller {
 
         // バリデーションエラー
         $validate = Validator::make($r->all(), [
-            'password' => 'required|min:8|max:72|confirmed|alpha_num',
+            'password' => ['required', 'min:8', 'max:72', 'confirmed', new \App\Rules\Hankaku],
         ]);
 
         if ($validate->fails()) {
diff --git a/backend/app/Http/Controllers/Api/FathersController.php b/backend/app/Http/Controllers/Api/FathersController.php
index 8561db3f..ce4e9f2d 100644
--- a/backend/app/Http/Controllers/Api/FathersController.php
+++ b/backend/app/Http/Controllers/Api/FathersController.php
@@ -167,7 +167,7 @@ class FathersController extends Controller {
 
         $validate = Validator::make($r->all(), [
             'token' => 'required',
-            'password' => 'required|min:8|max:72|confirmed|alpha_num',
+            'password' => ['required', 'min:8', 'max:72', 'confirmed', new \App\Rules\Hankaku],
             'company' => 'required|max:100',
             'image' => 'image_size|image_meme',
             'profile' => 'max:1000',
@@ -479,7 +479,7 @@ class FathersController extends Controller {
 
         // バリデーションエラー
         $validate = Validator::make($r->all(), [
-            'password' => 'required|min:8|max:72|confirmed|alpha_num',
+            'password' => ['required', 'min:8', 'max:72', 'confirmed', new \App\Rules\Hankaku],
         ]);
 
         if ($validate->fails()) {
diff --git a/backend/app/Rules/Hankaku.php b/backend/app/Rules/Hankaku.php
new file mode 100644
index 00000000..511a70f6
--- /dev/null
+++ b/backend/app/Rules/Hankaku.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace App\Rules;
+
+use Illuminate\Contracts\Validation\Rule;
+
+class Hankaku implements Rule {
+    public function __construct () {
+        //
+    }
+
+    public function passes ($attribute, $value) {
+        return preg_match('/^[a-zA-Z0-9]+$/', $value);
+    }
+
+    public function message () {
+        return trans('validation.alpha_num');
+    }
+}