To improve heat dissipation efficiency by a heat dissipating portion relative to a heat receiving portion contacting an inner peripheral surface of belts while effectively utilizing spaces in the belts forming a nip in which a recording material is cooled, where heat sinks 53 and 54 are disposed on and under upper and lower belts 51 and 52, heat absorbing portions 53a and 53b (contact portions with the belts) are provided by being shifted in a sheet feeding direction so as not to contact each other through the belts, but heat discharging portions 53c, 53d, 54c, and 54d are disposed in an extended manner so as to overlap with the heat absorbing portions on opposite sides. Thus, it becomes possible to enhance heat dissipation efficiency in spaces in limited belt cross sections, and to meet downsizing and speed-up of the device.