PURPOSE: To uniform the distribution of plasma density in the substance to be processed by providing the ends, on the processing chamber side, of exhaust gas tubes, which connect a processing chamber with a vacuum pump, in plural numbers such that they surround a semiconductor substrate being arranged.

CONSTITUTION: A grounded disc-shaped lower electrode 3 is fixed to the top of a supporting member 1 which is engaged with the rotary shaft of a motor, and above that a disc-shaped upper electrode 5, which is connected to a high frequency power source 4, is provided opposite to the lower electrode. The upper electrode 5 is of hollow structure, and has a number of gas passage holes 7 at the surface facing the lower electrode 3, and is coupled to a gas supply tube 9. Around the lower electrode 3, a processing chamber wall 19 made of aluminum is provided, which forms a lower housing, and below the processing chamber wall 9, for example two pieces of exhaust gas tubes 49 and 50 are provided in positions which are opposed 180°, and the exhaust gas tubes 49 and 50 join each other in the middle and it is coupled to a vacuum pump 52 through a pressure control valve 51. Hereby, maldistribution of exhaust gas flow inside the processing chamber is prevented, and the plasma treatment of the substance to be processed can be made uniform.