As a means to reduce exhaust emission, narrowing nozzle hole diameter is known to be an effective method of improving fuel atomization. In general, Electrical Discharge Machining (EDM) is more effective than other machining techniques because there is no burring and no machining force is apply to the tool, but the drawback to EDM is a low removal rate. An EDM drilling device by using piezoelectric elements has been newly developed. This device can drive a wire electrode at a high response of 5kHz. As a result of high response, this device can drill holes 0.1-0.5mm in diameter 3 times more efficiently than a conventional electrical discharge machine.