In a conventional image forming apparatus, there is a problem in which setting information cannot be changed in power-saving mode. An image forming apparatus F1 includes an interface unit F12 that transmits and receives signals to and from a PC client even in power-saving mode, an information storage unit F14 that is supplied with power to become responsive when a request for changing a setting state is provided, and an SNMP control unit F11 that controls the information storage unit F14 upon request from the PC client. Therefore, by starting the information storage unit F14, it is possible to change the setting information, such as a specified emulation of the image forming apparatus and user account information recorded on the information storage unit F14 of the image forming apparatus F1. Also, in conventional technology, in order to check whether a setting-information changing function unit of the image forming apparatus is in a startup state, an external terminal device has to repeatedly make an inquiry until a functional unit of changing the setting information of the image forming apparatus becomes in a startup state. This problem is solved by providing a function of replying with a time until startup in response to an inquiry from the external terminal device and a function of reporting a difference in power mode among functional units.