PURPOSE: To facilitate secure shielding of electromagnetic wave generated by a plasma and, etc., by a method wherein a conductive member connecting between a first housing and a second housing electrically is provided.

CONSTITUTION: A treatment chamber wall 19 made of aluminum is provided around a lower electrode 3 to form a lower housing. An electromagnetic wave shielding cover 21 which is made of aluminum or stainless steel and in which an upper electrode 5 is housed is provided above the lower housing to form an upper housing. A packing 23 is provided on the top end surface of the treatment chamber wall 19 and the lower surface of the electromagnetic shielding cover 21 is so provided as to touch the packing 23 air-tightly and, at the same time, a conductive elastic member such as an embossed tape 25 having a copper layer is provided between the facing surfaces of the upper housing and the lower housing. With this constitution, the upper housing is securely connected to the lower housing electrically and, by grounding one of the housings, an electromagnetic wave generated by a plasma and, etc., can be securely shielded.