a discharge machining apparatus includes an electrode disposed in confronting relation to a workpiece with an insulative machining solution interposed therebetween for machining the workpiece by an electric discharge generated across an interelectrode gap between the electrode and the workpiece , a detector device for detecting a distribution of times to generate the discharge across the interelectrode gap after a voltage has been applied thereacross , and interelectrode condition discriminator for comparing a distribution of times as detected by the detector means after the voltage has been applied across the interelectrode gap and before the discharge is generated thereacross to produce a signal indicative of a determined condition of the interelectrode gap .