A workpiece mounting table (20) for an electric discharge machine, which machines a workpiece (12) by discharging electricity between an electrode and the workpiece (12) in an interior of a work tank (6) and removing a surface of the workpiece (12), includes a surface-plate mounting table (3) made of a conductive material and arranged at the bottom of the work tank (6), a plurality of insulating materials (2), each of which has a flat shape and is arranged and fixed on the surface-plate mounting table (3) with a gap (4) between the insulating materials (2) to constitute an insulating flat plate (30), and a surface plate (1) made of a metal material, fixed on the insulating flat plate (30) and insulated from the surface-plate mounting table (3) by the insulating flat plate (30), for fixing thereon the workpiece (12).