A fuser, having a heater, a holder, and a first wire spring, is provided. The heater is in a form of a planar plate and has a first face and a second face. The holder has a supporting base supporting the first face of the heater. The first wire spring retain the heater on the holder. The first wire spring has a first facing portion, a first engageable portion, and a second engageable portion. The first facing portion faces and supports the second face of the heater. The first engageable portion and the second engageable portion extend from one and the other ends of the first facing portion. The first engageable portion and the second engageable portion are engageable with the holder in an end area on one side and an end area on the other side of the heater in a widthwise direction.