An image fusing apparatus includes a heating belt including a resistance heating layer, an insulating layer formed on an inner surface of the resistance heating layer, and a release layer formed on an outer surface of the resistance heating layer; a heating supporting roller disposed (positioned) inside the heating belt and rotating with the heating belt; a pressing roller disposed (positioned) parallel to the heating supporting roller and in contact with the outer surface of the heating belt to form a nip; and an electricity supplying member to supply electricity to the resistance heating layer of the heating belt. A thickness of paper non-contact areas of opposite side end portions of the resistance heating layer of the heating belt is the same as or thicker than the thickness of a paper contact area of a middle portion of the resistance heating layer thereof.