PURPOSE: To prevent generation of abnormal heating on any portion at the time of energization to a heater wire by forming a heater groove through filling of an electrically insulating material into a groove formed on the back of a heating plate, inserting a member which is formed by winding the heater wire on a core member of inorganic fiber thereinto, and applying the electrical insulating material thereon.

CONSTITUTION: The back of a metal heating plate 1 is charged with an electrical insulating material to form a first charge layer 4 on which a heater groove 4a is formed. A member which is formed by winding a heater wire 3 around a core member 2 made of inorganic fiber and provided with a terminal 6 is inserted into the groove 4a, and the electrical insulating material is charged onto the layer 4 and the wire 3 to provide a second charge layer 5. The inside of the wire in the form of coil is charged with the core material 2 at the time of producing the plate 1 in this manner, and the wire 3 is buried in the electrically insulating material. It is thus possible to prevent generation of abnormal heating at the wire 3 at the time of energization to the wire as there is no generation of abnormal heating on any portion.