A process and apparatus for controlling an electric discharge machine consisting of applying a pulse voltage across a working gap when the predetermined time of interruption of the electric discharge has lapsed and when the interpolar voltage has exceeded a reference voltage, increasing the reference voltage and lengthening the time of interruption of the electric discharge when the rate of abnormal discharge occurrence becomes greater than an allowable rate and decreasing the reference voltage and reducing the time of interruption of the electric discharge when the rate of abnormal electric discharge occurrence is less than an allowable rate.