PURPOSE: To remove temperature nonuniformity inside a heating chamber so as to enable remarkable shortening of the time required for temperature rise by forming a heating chamber wall out of ferromagnetic substance and supplying current converted into high frequency to a coil provided at the outside of the wall.

CONSTITUTION: The walls 2, 2' of a heating chamber 1 is formed of ferromagnetic substance metal and heating coils 4, 4' arranged at the outside of the walls 2, 2' are supplied with high frequency current of commercial current converted with an inverter. Hereby, the coils 4, 4' are applied with alternate magnetic field and induction heating is generated in the walls 2, 2' by the hysteresis of the magnetic field and the temperature inside the heating chamber 1 rises in the remarkably short time with small effect of infrared radiation and without temperature nonuniformity. Further, the induction heating is also selectable through a magnetron 6.