A coil spring 60 is provided in an empty room (inside of a fixing roller 50) of a main body 52 of a roller. The coil spring 60 is in contact with an inside wall 52a surrounding the empty room of the roller main body 52 and pushes the inside wall 52a outward. The coil spring 60 and the inside wall face 52a are coated with a black film 66 except the contact portion 62 of the coil spring 60 and the inside wall 52a.