For a plasma processing apparatus that performs an etching process for the face of a wafer opposite the circuit formation face, ceramic insulating films having a ring shape are positioned on the mounting face of an electrode member in consonance with the location of a large wafer or a small wafer. When a large wafer is employed, a ring member is attached. And when a small wafer is employed, a blocking member is mounted to hide a gap between the insulating films deposited on the mounting face 3b and to cover suction holes. Further, a cover member is attached to cover the blocking member from the top. With this arrangement, the plasma process can be performed, using the same electrode member, for wafers having different sizes.