Components such as an earth plate, a gas introduction ring, and the like placed in a reaction chamber in a plasma apparatus are made of aluminum containing magnesium in a concentration of 2.2 to 2.8% by weight and are not coated with alumite. In addition, a heater incorporated in a section of the reaction chamber heats the section during a plasma cleaning process. Further, an electrical discharge chamber is also incorporated in the plasma apparatus for providing a plasma to the reaction chamber for efficient plasma cleaning of the apparatus.