In a device for fusing a toner image on a recording medium, a first roller provided with a heat source and a second roller are provided. A stretcher is elongated in a longitudinal direction of the second roller. An endless belt is stretched by an outer circumferential face of the second roller and a first face of the stretcher, and circulated in accordance with rotation of the first roller and the second roller. The endless belt is sandwiched between the first roller and the second roller to form a nipping portion through which the recording medium passes to fuse the toner image thereon. A supporter is disposed between the second roller and the stretcher. The supporter is elongated in the longitudinal direction of the second roller, and is provided with at least one first projection having a first face which is brought into slide contact with at least a longitudinal center portion of the outer circumferential face of the second roller.