diff --git a/resources/views/layouts/app.blade.php b/resources/views/layouts/app.blade.php
index c2e482bd3..028416cb1 100644
--- a/resources/views/layouts/app.blade.php
+++ b/resources/views/layouts/app.blade.php
@@ -48,6 +48,13 @@
     if (isset($page)) {
         $page_tree = app('request')->attributes->get('page_tree');
         $meta_robots = $page->getMetaRobots($page_tree);
+    } elseif ($is_manage_page || in_array(\Route::currentRouteName(), [
+        'show_login_form', 'login',
+        'show_register_form', 'register',
+        'register.confirmToken', 'register.storeToken',
+        'password.request', 'password.reset',
+    ])) {
+        $meta_robots = 'noindex, nofollow';
     }
 @endphp
 @if ($meta_robots)
diff --git a/tests/Feature/Auth/NoIndexMetaRobotsTest.php b/tests/Feature/Auth/NoIndexMetaRobotsTest.php
new file mode 100644
index 000000000..001bf8f1b
--- /dev/null
+++ b/tests/Feature/Auth/NoIndexMetaRobotsTest.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace Tests\Feature\Auth;
+
+use App\Models\Core\Configs;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+/**
+ * ログイン・ユーザー登録・パスワード再設定の各画面が、検索エンジン向けに
+ * noindexを出力し続けることを守る。Route::currentRouteName()による判定は
+ * ルート名変更時に静かに機能しなくなるため、回帰検知の目的で用意する。
+ */
+class NoIndexMetaRobotsTest extends TestCase
+{
+    use RefreshDatabase;
+
+    private const NOINDEX_TAG = '<meta name="robots" content="noindex, nofollow">';
+
+    public function testLoginPageHasNoIndexMetaRobots()
+    {
+        $response = $this->get('/login');
+
+        $response->assertOk();
+        $response->assertSee(self::NOINDEX_TAG, false);
+    }
+
+    public function testRegisterPageHasNoIndexMetaRobots()
+    {
+        Configs::factory()->create([
+            'category' => 'user_register',
+            'name' => 'user_register_enable',
+            'value' => '1',
+            'additional1' => 1,
+        ]);
+
+        $response = $this->get('/register');
+
+        $response->assertOk();
+        $response->assertSee(self::NOINDEX_TAG, false);
+    }
+
+    public function testPasswordResetPageHasNoIndexMetaRobots()
+    {
+        Configs::factory()->create([
+            'category' => 'base',
+            'name' => 'base_login_password_reset',
+            'value' => '1',
+        ]);
+
+        $response = $this->get('/password/reset');
+
+        $response->assertOk();
+        $response->assertSee(self::NOINDEX_TAG, false);
+    }
+}