A plasma processor with a microwave generating source mounted integrally on a shield lid by miniaturizing a matching circuit. The plasma processor is characterized by comprising a evacuatable processing vessel (42), a workpiece mount base (44) provided in the processing vessel, a microwave transmitting plate (70) provided in the opening section of the top of the processing vessel, a plane antenna member (74) for supplying a microwave into the processing vessel via the microwave transmitting plate, a shield lid (78) so grounded as to cover the top of the plane antenna member, a waveguide (82) for guiding the microwave from a microwave generating source to the plane antenna member, a member elevating mechanism (85) for relatively varying the vertical distance between the plane antenna member and the shield lid, a tuning rod (104) so provided insertably into the waveguide tube, a tuning rod drive mechanism (102) so moving the tuning rod as to adjust its insert amount, and a matching control section (114) for matching adjustment by controlling the elevation amount of the antenna member and the insert amount of the tuning rod.