To provide a technology for not placing an induction heating coil above a workpiece in a high-temperature state.

The induction heating coils 111 and 112 that are divided into two parts and have such a shape as to surround a cylindrical furnace shell 105, wherein a to-be-heated material is stored, from a side face thereof, are displaced. By moving the induction heating coils 111 and 112 horizontally with respect to the furnace shell 105, movement to a place where induction heating is conducted and receding from there are performed. Thus, location of the induction heating coils 111 and 112 above the furnace shell 105 can be prevented to avoid a situation in which the induction heating coils 111 and 112 are heated above the furnace shell 105.