A heat roller having a cylindrical sheet-like heating element having a resistance member embedded into an insulating member. The sheet-like heating element is arranged between an inner tube and an outer tube. The resistance member is formed such that a heating density of the sheet-like heating element is changed in an axial direction of the heat roller. The heating density of the sheet-like heating element at its edge section is greater than that at a center in the axial direction of the heat roller.