A fixing device includes an endless belt, a nip member having a contact surface that is in contact with the inner surface of the endless belt, a backup member configured to pinch the endless belt in conjunction with the nip member, an upstream guide disposed upstream of the nip portion in the rotating direction, and a regulating portion. The upstream guide and the nip member are disposed while a first gap is provided, in a conveying direction of the recording sheet, between a middle portion of the upstream guide and a middle portion of the nip member. The regulating portion and one of the upstream guide and the nip member are disposed while a second gap is provided therebetween in the conveying direction of the recording sheet. The second gap is smaller than the first gap in the conveying direction of the recording sheet.