PURPOSE: To heat at a good heating efficiency, and to reduce the using amount of a heating element wire and the using amount of an adiabatic layer, by holding the heating element wire at the inner side of the adiabatic layer by making the apex of the heating element wire whose section form is a triangle, which heat-treats a wafer, at the adiabatic layer side.

CONSTITUTION: At the inner side of an adiabatic layer 2, an element wire holder 5 is held to make the apex of a heater element wire 3 whose section form is a triangle, which heat-treats a wafer 7, at the adiabatic layer 2 side, and the inner side of the adiabatic layer 2 is made in a white color system. A radiant heat is discharged from the bottom surface of the element wire 3 to the wafer 7 at the inner side, it is reflected by the white color system of the inner surface of the adiabatic layer 2, and it advances to the wafer 7 at the inner side, and as a result, a heating member is used effectively to heat the wafer 7. Since the radiant heat advancing to the adiabatic layer 2 is utilized to the heat treatment of the wafer 7 at the white color system of inner surface, the winding intervals of a winding 3 can be reduced. Consequently, since the radiant heat 8 from the element wire 3 is discharged only in three directions, and the radiant heat 8 advancing to the outer side is reflected and turned to the inner side, one wafer 7 can be heated at a good heating efficiency.