which a top plate 54 is provided for receiving a cooking pan 53 the heating coil 9 is provided at the underside of the top plate 54 so as to be close thereto operation of the load applicability detecting circuit 15 will now be described in the circuit arrangement described above when the inverter 7 is not driven that is when the induction heating operation is not executed the level difference between the output signal e18 from the input current detecting means 18 and the reference signal e28 from the reference signal generating means 28 is maintained at a constant value with the relation of e18 gt e28 as is understood from f and g of fig4 illustrating signal waveforms at various points a g in the circuit shown in fig2 the voltage level at each point in fig2 is shown as that at time point t1 in fig4 in the initialized state that the power supply switch 2 is turned on to supply each circuit with the control power at time point t1 an output signal e18 from the input current detecting means 18 and a reference signal e28 from the reference signal generating means 28 are supplied to the comparator 41 of the comparator means 40 since the level of the output signal e18 is higher than that of the reference signal e28 the output of the comparator 41 is turned to the high level consequently the integrating circuit 45 starts its integration operation as shown by fig3 d and gradually.