An image forming apparatus which is started in a plurality of modes and improved in reliability of the firmware update function. An image forming apparatus includes a storage unit that stores standard firmware for a normal operation and safe firmware for updating the standard firmware, in respective different storage areas. A standard firmware update section updates the standard firmware. Proper operations of the standard firmware update section and the safe firmware update section are verified before updating them, respectively. When the verification of the operation of the standard firmware update section is successful, the standard updating section is caused to perform the update of the standard firmware. When the verification of the operation of the safe firmware update section is successful, the safe firmware update section is caused to perform the update of the safe firmware.