Recently, technology of electric discharge machining has been making rapid progress. Electric discharge machining is classified into two types based on power supply system: a capacitor type and a transistor type. Because performance of electrode varies depending on the type of power supply, material quality of work to be machined and discharging conditions, special care should be taken in selecting an electrode. For the raw materials of electrode, there are copper-tungsten alloy, silver-tungsten alloy, copper, brass, graphite, copper-graphite, aluminum and iron. The copper tungsten alloy (EM-C30A2) and silver tungsten alloy (EM-S35A) show excellent performance in a machining required severe surface accuracy and dimensional accuracy for a machined surface. Especially, EM-C30F2, -C30H2, and -S35H2 are highly evaluated for their excellent machining performance to steel and cemented carbide.