An image forming apparatus includes an image forming section, a fixing device, and circuitry. The image forming section forms an image on a recording medium. The fixing device includes a rotator including a flexible endless belt, a pressure rotator pressed against the rotator to form a nip between the rotator and the pressure rotator, a heater heating the rotator, and a movable shield. The movable shield is disposed between the heater and the rotator to shield the rotator from radiant heat generated from the heater and is movable according to a size of the recording medium. The circuitry is configured to control the image forming section to form the image on the recording medium based on an image forming condition and change at least one of an operating temperature of the movable shield or a shielding amount of the movable shield based on the image forming condition.