PURPOSE: To provide the current waveform which is constantly suitable for the electric discharge machining during the electric discharge machining operation by providing a feedback part to output the control signal to the electric discharge machining control device on the basis of the data from the judgment part.

CONSTITUTION: The wave height value and the pulse length of the current waveform during the electric discharge machining operation are detected and the difference between the detected values and the target values are judged by a judgement part 14. The data which are preliminarily stored are read out on the basis of the judged results, and the voltage value of the DC power source and the ON-time of a switching element are controlled by the feedback part 15, keeping the current waveform at the desired target value. Thus, the current waveform which is cosntantly suitable for the electric discharge machining during the electric discharge machining operation is obtained, and the efficient electric discharge machining can be executed from the beginning to the end of the operation.