Abstract: In a heat roll consisting of a mandrel and a surface layer, this invention comprises a fixing apparatus and a recording apparatus, wherein a thickness of the surface layer is formed not exceeding the thickness determined by a square root of the product of a heat diffusion rate of the surface material and a nip time required for a form to pass a nip zone, and a thickness of the mandrel is formed not less than the thickness determined by a square root of the product of a heat diffusion rate of the mandrel material and a one rotational period of the mandrel. Since the surface layer and the mandrel are so specified for the thickness as mentioned, a quantity of heat flowing from the mandrel into the surface layer multiplies, and thus a high fixing strength is obtainable. The fixing apparatus and the recording apparatus are provided further with a cleaning device high in cleaning capacity.