Abstract: A convection heater 23 is disposed along a back surface of a rear face plate 18 which is comprised of a stainless steel plate that forms a heating chamber 14. On a back side of the rear face plate 18, disposed is a circulation fan 22 by which, air in the heating chamber 14 is sucked from air intake use through-holes into the back side, and after it is heated by the convection heater 23, it is returned from air blowing use through-holes to the heating chamber 14. On a surface of an inner side of the heating chamber 14 of the rear face plate 18, a self-cleaning layer is formed by dissolving a self-cleaning material which oxide-decomposes and removes accreted dirt at high temperature into a porcelain enamel glaze and by applying and bake-sticking.