First belt 51 suspended on first upstream roller 53 and first downstream roller 54, and second belt 52 suspended on second upstream roller 55 and second downstream roller 56 each have a stiffness such that when assumed to be separated from each other, the first belt 51 and the second belt 52 rotate while maintaining an elliptic shape thereof. One of two portions of the first belt 51 facing each other between the first upstream roller 53 and the first downstream roller 54 and one of two portions of the second belt 52 facing each other between the second upstream roller 55 and the second downstream roller 56 are flat as a result of being brought into pressing contact with each other, and a fixing nip is formed therebetween. A toner image is fixed by being heated by heater lamp 57 when recording sheet S passes through the fixing nip.