When a user uses one of a plurality of image forming apparatuses from one of a plurality of terminals, an authentication server determines, on a user by user basis, whether he/she is permitted to use each image forming apparatus, and detects if any of the image forming apparatuses is in a troubled state and incapable of executing a prescribed function. If one image forming apparatus is in a troubled state and the user requests another, trouble-free image forming apparatus to execute a job utilizing a function of the trouble-free image forming apparatus, the authentication server permits execution of the job if the user is permitted to use the image forming apparatus in the troubled state. Thus, the user can get a print even if a usually used image forming apparatus is unavailable.