An object is to provide an image processing apparatus which can reduce power consumption during the power saving standby mode. The starting factor monitor unit and the power saving standby mode voltage control unit are driven with the USB bus power can be supplied during a shift to the power saving standby mode and the starting factor monitor unit and the power saving standby mode voltage control unit are driven by voltage from the main power supply when the USB bus power cannot be supplied during a shift to the power saving standby mode.