Redirect issue in middleware for admin login in Laravel

When login to admin,then page is redirect But 'The page isn't redirecting properly' message show. Please help me

Middleware  - IsAdmin.php

    public function handle($request, Closure $next)
    {

         if (Auth::user()->role_id == 1)
        {
            return redirect ('/administrator');
        }

               return $next($request);
    }

web.php

Route::group(['prefix'=>'administrator','as' => 'admin.','middleware' => ['auth'],'middleware' => 'isAdmin'], function(){

    Route::get('/','AdminController@index');

    Route::resource('user','AdminController');

    Route::resource('card','AdminCardController');

});

Thanx in advanced..

via Chebli Mohamed