PURPOSE: To drop a high-frequency power efficiency to the surfaces other than the part with a matter to be treated, and to upgrade the same efficiency to the matter to be treated by a method wherein the constitution or the material of the electrode is made to differ in the part opposed to the matter to be treated from in the parts other than the part.

CONSTITUTION: An electrode main body 21 is formed of a good conductor, such as copper, and coolant flow paths 22 used as the cooling means are formed in the interior of the main body 21. A part whereon a matter 30 to be treated is placed, of the main body 21 is made into a protrusion and the parts other than the part are coated with materials other than copper, such as peripheral materials 23 consisting of a fluororesin. The surface part whereon the matter 30 to be treated is placed, of the main body 21 is coated with a material other than copper, such as an electrode coating material 24 far thinner than such a peripheral material as a polyimide resin. Hereby the electric resistances of the peripheral parts are more increased than that of the part of the matter 30 to be treated and high-frequency power is impressed in inverse proportion to the respective electric resistances. Accordingly a power efficiency to the matter 30 to be treated is significantly upgraded.