A plurality of plate-like workpieces held by a workpiece holder are subjected to discharge machining by a wire electric discharge machine. The workpiece holder includes a cylindrical member in which the plurality of plate-like workpieces are housed in a stacked state, lid members placed on upper and lower ends of the plate-like workpieces housed in the cylindrical member so as to press the plate-like workpieces, and a workpiece stage mount member having an insertion hole in which the cylindrical member is inserted and housed. Concave sections are formed in positions corresponding to a machining start point and a machining end point on an inner circumference surface of the cylindrical member.