A fixing device for an image forming apparatus having low heat losses. The fixing device consists of a fixing roller and a compression roller for abutting upon it under pressure. The fixing roller and compression roller have a release layer each formed on the surface of a core metal formed of an aluminum hollow cylinder. The release layer on the surface of the fixing roller is formed of a composite material of metallic powder of good thermal conductive material such as nickel, and fluorine resin such as polytetrafluoroethylene (PTFE) and polyphenylene alkoxyether (PFA), and has spectral emissivity at a wavelength of 5 to 10 .mu.m being within a range of 0.1 to 0.65. The compression roller is provided with a release layer formed of fluorine resin like the conventional one, or the same material as the release layer on the surface of the aforesaid fixing roller, having lower spectral emissivity.