PURPOSE: To improve surface roughness of a work, by changing machining fluid after electric discharge machining, performing electro-chemical machining through the same device and removing a denatured layer from an electric discharge machined surface.

CONSTITUTION: A wire cut electric discharge machining device comprises an insulating table 2, on which a work 1 is placed, wire an electric discharge machining power source DPS. An electro-chemical machining power source EPS and FET switching circuit Sc are further provided to said device, and a switch S, capable of switching from a position ac to a position bc at changeover from electric discharge machining to electro-chemical machining, is provided. In case of performing the primary machining, the switch S is placed to the position ac and a valve is opened, then the machining device performs electric discharge machining while supplying electric discharge machining fluid to the work 1. Then the valve is closed, and electro-chemical machining fluid is fed by a pump from a tank to a nozzle, simultaneously the switch S is selected to the position bc to perform electro-chemical machining.