Plasma is generated in a vacuum chamber (1) by supplying high frequency power to a spiral antenna (5) from an antenna-use high frequency power source (4) and by supplying high frequency power to an electrode (6) by an electrode-use high frequency power source (8) in a state where evacuating a vacuum chamber (1) while introducing a specified gas into the vacuum chamber, thereby controlling the vacuum chamber at a predetermined pressure. Plasma processing such as etching is performed on a substrate (7) located on the electrode (6), the interior of the vacuum chamber is heated to 80° C. or higher, wherein a resistance-heating heater (11) constituted of a heating element shielded from electromagnetic waves by a conductive sheath and a pressure-weld type thermocouple (10) provided on a dielectric body (9) are connected to a temperature adjuster (12). A insulating material (13) is arranged between the heater (11) and the antenna (5), and an inner chamber (16) including a belt heater (22) is also arranged.