UserController.php

<?php

namespace App\Http\Controllers\admin;

use App\User;
use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
use Illuminate\Support\Facades\Auth;

class UserController extends Controller
{
    /**
     * @param Request $request
     * @return \Illuminate\Http\RedirectResponse|\Illuminate\Routing\Redirector
     */
    public function login(Request $request)
    {
        $this->validate($request, [
            'email' => 'required|email|exists:users,email',
            'password' => 'required',
        ]);


        if ($user = Auth::attempt([
            'email' => $request->email,
            'password' => $request->password
        ])) {
            /** @var $user User */
            if ($user->isAdmin()) {
                return redirect()
                    ->route('admin.dashboard');
            }
        }

        return redirect('/admin/login');
    }
}

Great