Power source device for electric discharge machine

A power supply device for an electric discharge machine for supplying a pulsed current to an electrode gap constituted by a workpiece and an electrode, which are opposed to each other with a predetermined gap, for electric discharge machining a workpiece, the power supply device comprising:

• a DC power supply which is connected in parallel to the electrode gap for applying a voltage for generating the current to the electrode gap,
• a plurality of switching elements which are in parallel to each other and which are arranged between the electrode gap and the DC power supply,
• current value acquisition circuitry for acquiring a current value, and
• an ON-OFF controller which, during the time interval from the time when the current value reaches a predetermined value to the starting time of a fall of the current value, sets a cycle for switching the plurality of switching elements from off to on to be the same cycle, switches the plurality of switching elements from off to on in sequence for each timing of a phase of a predetermined angle, sets an ON-period of each of the plurality of switching elements based on a difference between the current value and the predetermined value, and performs ON-OFF control of the plurality of switching elements based on the cycle, the timing, and the ON-period.