An image forming apparatus is configured to receive user authentication information and perform image formation based on an image formation request and is connected to an external authentication server which performs authentication based on the user authentication information. The image forming apparatus comprises an authentication querying unit that queries the external authentication server for the authentication based on the user authentication information; an authentication result receiving unit that receives a result of the authentication performed by the external authentication server; an authentication result storage unit that stores the result of the authentication received by the authentication result receiving unit; and a control unit that controls the authentication querying unit, the authentication result receiving unit, and the authentication result storage unit. When the image forming apparatus receives the user authentication information, the control unit performs the authentication based on the result of the authentication stored in the authentication result storage unit.