An input part sets either a charge time zone or a discharge time zone. A first firmware storage part stores first firmware defining all operation contents of a power supply device. An acquiring part acquires second firmware that is firmware for update, and a second firmware storage part stores the second firmware. A controller refers to the charge time zone, the discharge time zone and the like received from the input part to extract a first time zone in which neither the charge time zone nor the discharge time zone is set. The controller preferentially sets timing for updating firmware in the first time zone.