PURPOSE: To heat a material to be heated to a uniform temp. over the entire surface when the material is directly heated by supplying electric current, by heating the surface of the material with auxiliary heating means.

CONSTITUTION: A material 3 to be heated is placed on refractories 5 for supporting a material to be heated in a resistance heating furnace 1 and an atmospheric gas is fed to the furnace 1. Electrodes 4 are brought into contact with ends of the material 3 and electric current is supplied to heat the material 3. During this heating, the surface of the material 3 is supplementally heated with heaters other than resistance heaters, e.g., heating elements 7-1 or burners so as to compensate the radiation of heat from the surface of the material 3.