转到 App\Http\Middleware\RedirectIfAuthenticated 然后从

public function handle($request, Closure $next)
{
    if ($this->auth->check()) {
        return redirect('/home');
    }

    return $next($request);
}

到

public function handle($request, Closure $next)
{
    if ($this->auth->check()) {
        return redirect('/admin');
    }

    return $next($request);
}