In one embodiment, when a hot roller is driven to rotate, a driving gear rotates so that a swing gear and a swing cam rotate. Then, a sliding contact edge on the right side of a swing lever that abuts against the circumferential face of the swing cam repeatedly moves up and down, and the swing lever repeatedly rotates clockwise and counterclockwise with a shaft of a pressure release cam as the center. At this time, since only the clockwise rotation of the swing lever is transmitted via a one-way clutch to the shaft of the pressure release cam, the clockwise rotation is intermittently transmitted to the shaft of the pressure release cam. As a result of this, the pressure release cam intermittently rotates clockwise, and the pressure release cam pushes away a roller of a displacement frame, so that the pressure roller separates from the hot roller.