PURPOSE: To allow induction heating of a work disposed in a heating coil closely thereto by operating a single transistor as a current regenerating inverter for inducing high frequency current in the secondary coil of a transformer.

CONSTITUTION: A transistor drive circuit 6 turns a transistor 7 ON/OFF to feed a resonance current of a capacitor 9 and the primary coil 4a of a transformer 4 thus inducing an AC high frequency current in the secondary coil 4b of the transformer 4. The high frequency current is fed to a heating coil 12 for induction heating a work 13. In this regard, current flowing through the circuit is detected by means of a resistor 11 and fed to a transistor drive circuit 6 in order to control the output to a predetermined level. This constitution allows reduction in the size and weight of a transistor inverter unit 1 and further downsizing is realized by employing an IGBT 5 comprising moduled transistors 7 and diodes 8.