Electrically conductive CVD diamond having a high thermal diffusivity, when used as an electrode for micro EDM, revealed very low wear compared to copper and Cu-W electrodes in the case of finish EDM condition, where the short pulse duration is adopted. In this research work polycrystalline diamond (PCD), which has a thermal conductivity similar to that of the electrically conductive CVD diamond, is introduced as a new composite electrode material for EDM. Various properties of PCD with respect to EDM of die-steel (SKD11) and tungsten carbide (G5) have been studied and compared with those of the electrically conductive CVD diamond, copper and copper-tungsten electrode materials. It is found that electrode wear and material removal rate decreased with an increase in thermal conductivity depending on the type of the PCD material when very short pulse duration of te=1µs is applied. Extremely low wear, 1/20~1/50 times of the Cu-W electrode in the case of EDM of tungsten carbide workpiece at short pulse duration and zero wear in the case of EDM at short and long pulse duration of SKD11 can be realized.