A fixing device includes a belt, a roller, a heater, and a reflector. The belt is rotatable in a rotational direction. The roller is positioned to be in contact with an outer peripheral surface of the belt so as to form a nip between the roller and the belt. The heater is disposed within an inner circumference of the belt. The reflector is configured to reflect heat generated by the heater toward an inner surface of the belt. The reflector includes a first portion that is in contact with the belt at a first region downstream with respect to the nip in the rotational direction. The first portion causes a curvature of the belt at the first region to be greater than the curvature of the belt at regions of the belt adjacent to the first region.