How to send multiple attachment to mail in Laravel?

The Illuminate\Mail\Mailable::attach() method returns $this, you just have to chain it:

/**
 * Build the message.
 *
 * @return $this
 */
public function build()
{
    return $this->view('emails.orders.shipped')
                ->attach('/path/to/file', [
                    'as' => 'name.pdf',
                    'mime' => 'application/pdf',
                ])
		->attach('/path/to/another/file')
		->attach('/path/to/a/third/file');
}