Patent ID: 7795558

Claim:
An electric discharge machine that machines a workpiece by using a water-based dielectric fluid as a dielectric fluid while a voltage is being applied to a machining gap between an electrode and the workpiece, the electric discharge machine comprising: an anticorrosive power source section that applies a predetermined voltage by taking the workpiece as a cathode and taking as an anode an anticorrosive electrode opposing the workpiece with an electrical insulator between the workpiece and the anticorrosive electrode; a dielectric fluid quality measuring instrument that measures a quality of the dielectric fluid; and a dielectric fluid quality control section that controls a pH level of the dielectric fluid to be within a range from 8.5 to 10.5 on the basis of the measured quality of the dielectric fluid, wherein the dielectric fluid quality measuring instrument includes a conductivity meter that measures a conductivity of the dielectric fluid.