A power source for electric discharge machining employing a capacitor discharge circuit with charging and discharging switching elements 01, Q2 for use in an electric discharge machining apparatus, wherein no resistance for limiting charging current is used in order to eliminate energy loss and to prevent the switching element Q1 from breaking due to surge voltage of the switching element Q1. Further, a diode D is provided in parallel with the discharging capacitor C1. The diode D, the charging switching element Q1, and a capacitor C2 for smoothing the power source are fabricated in the form of a printed circuit board in order to reduce the stray inductance and to limit surge voltage.