An image forming apparatus orientatable in either a first position or a second position, the second position being different from the first position in inclination with respect to a horizontal plane, including a fixing unit including a fixing roller and a pressurizing roller, pressing the pressurizing roller against a surface of the fixing roller to form a fixing nip, and thermally fixing a toner image on a recording sheet passing through the fixing nip; at least one temperature sensor detecting surface temperature of the fixing roller without contact with the surface; a heater heating the fixing roller; and a controller controlling the heater according to the surface temperature, thereby controlling the surface temperature, wherein a heat sensitive portion of the temperature sensor is located above a horizontal plane passing through a rotational axis of the fixing roller regardless of the orientation of the image forming apparatus.