PURPOSE: To maintain the stable electric discharge state by embedding an electrode member made of a material different from that of an electrode main part into a groove formed in the axial direction of a rod-shaped electrode and revolving the electrode.

CONSTITUTION: An article 2 to be worked which is loaded on an X-Y table 3 is supplied with working liquid 8 and worked by an electrode 1 revolved by a motor M3. A groove in cruciform section is formed in the axial direction from the top edge part, of the electrode 1, and an electrode material made of a material different from that of the electrode material of a main part, namely graphite etc. is embedded into the groove. Working fluid is stirred and scattered through the revolution of the electrode, and discharges cutting powder etc. in the working gap. As the part made of a different material from that of the electrode material of the main part is formed at the top edge of the electrode, the electric discharge having different characteristics is performed after transition to the different working position because of the revolution of the electrode, and concentration of electric discharge to a specific point is prevented.