A heating unit includes a cylinder which rotates about an axis parallel to a first direction. A heater has a first surface abutting on an inner surface of the cylinder at a nip position. A support member is on a second surface of the heater and also contacts the cylinder. A first heating element is in the heater at a first position along the first direction. A second heating element in the heater is at a second position spaced from the first position. A first temperature sensor is above the first position. A locking portion of the heater is at a third position along the first direction. The locking portion engages the support member and restricts movement of the heater in the first direction. The first position is near a first outer edge of the cylinder. The second position is closer to a central portion of the cylinder.