Laravel Auth::attempt alway return false - laravel

Question

I don't know why Auth:attempt alway return false.
Here is my controller:
public function login(Request $request)
{
$this->validate($request, [
'email' => 'required|email',
'password' => 'required|min:6'
]);
$user = [
'email' => $request['email'],
'password' => bcrypt($request['password']),
];
if (Auth::guard('admin')->attempt($user)) {
return redirect()->intended(route('admin.dashboard'));
}
return back()->withInput($request->only('email', 'remember'));
}
Here is my Model:
use Notifiable;
/**
* The attributes that are mass assignable.
*
* #var array
*/
protected $fillable = [
'name', 'email', 'password',
];
/**
* The attributes that should be hidden for arrays.
*
* #var array
*/
protected $hidden = [
'password', 'remember_token',
];
/**
* The attributes that should be cast to native types.
*
* #var array
*/
protected $casts = [
'email_verified_at' => 'datetime',
];
public function setPasswordAttribute($value) {
$this->attributes['password'] = bcrypt($value);
}
Here is my route:
Route::group(['prefix' => 'admin'], function () {
Route::get('login', 'Admin\LoginController#showLoginForm')->name('admin.login');
Route::post('login', 'Admin\LoginController#login')->name('admin.login.post');
Route::get('logout', 'Admin\LoginController#logout')->name('admin.logout');
Route::group(['middleware' => ['auth:admin']], function () {
Route::get('/', function () {
return view('admin.dashboard.index');
})->name('admin.dashboard');
});
});
In controller i get array from html to send. But when in if (Auth::guard('admin')->attempt($user)) is alway false. I don't know why.
Please help me.
Thank so much.