A fixing device includes a heating element disposed inside a flexible fusing member, a nip member disposed to contact with a surface of the flexible fusing member and to allow the flexible fusing member to slide along the nip member, a reflecting plate for reflecting radiant heat from the heating element toward the nip member, and a backup member for nipping the flexible fusing member with the nip member. The reflecting plate includes a central reflecting portion extending along a longitudinal direction of the heating element at least in a region corresponding to along a heat generating portion of the heating element, and end reflecting portions stationarily provided on both ends of the central reflecting portion. The end reflecting portions are disposed in positions longitudinally outward of the heat generating portion and each has a reflecting surface tilted with respect to the longitudinal direction of the heating element.