To prevent mutual interference owing to a common high-frequency power where the directions of the lines of magnetic force of a plurality of induction heating coils are identical, enhance the heater efficiency, simplify the configuration, allow easy handling, and heighten the reliability.

One or more common high-frequency power generating devices 15 are furnished, and a plurality of controllers 7 are furnished to control the common high-frequency powers supplied from the generating devices 15 to respective induction heating coils 3 to their specified values, and a plurality of operating units 17 are furnished to operate so that the specified high-frequency powers given by the controllers 7 are supplied to the respective coils 3 independently. The coils 3 are divided in a plurality of groups, and the specified high-frequency powers are supplied group by group, and the output wiring of a high-frequency power supply device 15 is made a common bus, whereon the operating units 17 are mounted.