A fuser includes a rotatable member, a belt, a pressure member, and a sliding member. The pressure member sandwiches the belt together with the rotatable member to form a nip portion. The sliding member is sandwiched between an inner peripheral surface of the belt and the pressure member. The sliding member includes a front surface, which faces the inner peripheral surface of the belt. The front surface includes a plurality of first dimples and a plurality of second dimples. The first dimples are arranged in a zone corresponding to a first part of the nip portion. The second dimples are arranged in a zone corresponding to a second part of the nip portion, to which a pressure smaller than a pressure applied in the first part is applied. Each of the first dimples is of a shape that can release lubricant more easily than each of the second dimples.