An image forming system according to one embodiment of the present invention has a user authentication mode for granting only authorized users a setting change for an image forming apparatus. This image forming apparatus 200 includes a user authentication section 203 to perform authentication on receiving user information from a host computer 100. The image forming apparatus 200 also issues an authentication key for an authorized user and sends the key to the host computer 100. The host computer 100 sends a changed setting and the authentication key to the image forming apparatus 200, whereby making the setting change swiftly. This structure makes it possible to address a problem with related art systems that send user information every time a setting is changed and send a changed setting only when a user is deemed to have authority where authentication is redundant and time consuming.