An information processing system includes an information processing device, an image forming device, an authentication server performing authentication of a user and a relay server receiving an authentication request from the image forming device and establishing data communication with the authentication server. The information processing device attaches authentication information set in advance in a printer driver to the print job and sends to the image forming device, while sending user information indicating that the user is successfully authenticated in the authentication server to the relay server. The relay server identifies the user information received from the information processing device based on the authentication information included in the received the authentication request and establishes data communication with the authentication server based on the identified user information, thereby verifying if the user is a registered user and sending the response to the authentication request to the image forming device.