In a case where only one image forming apparatus ID stored in a PC coincides with an own ID of an image input/output system itself stored in this system, it is controlled to set up the option function of the image input/output system according to information concerning validation and invalidation of an option function of the image input/output system instructed on the PC side, while in a case where only one image forming apparatus ID does not coincide with the own ID of the image input/output system itself, it is controlled not to set up the option function of the image input/output system according to the information instructed on the PC side, thereby preventing that a user unfairly duplicates a setup program with an evil intention, and thus can set up the option function to the plural image forming apparatuses by purposely duplicating the setup program.