PURPOSE: To provide a plasma processing device which is equipped with a shielding plate that is less deformed and produces less contaminants.

CONSTITUTION: A plasma processing device is equipped with a reaction chamber 4 where reactive gas is turned plasmatic by microwaves 2, a wafer processing chamber 7 which processes the surface of at semiconductor wafer 8, and a insulating shielding plate 5 which separates the reaction chamber 4 from the processing chamber 7. The insulating shielding plate 5 prevents ions generated from plasmatic reactive gas from penetrating into the reaction chamber 4 but introduces radicals generated from plasmatic reactive gas into the reaction chamber 4, and furthermore, a mesh provided to the insulating shielding plate 5 is replaced with a finer mesh, whereby ions are stopped from passing through the insulating shielding plate 5. A quartz plate is used as a shielding plate which hardly contaminates the reaction chamber, and a composite shielding plate, which is composed of an aluminum plate and a quartz plate, not only grounds ions but also protects the reaction chamber against contamination and enables the aluminum plate to absorb ions that pass through the shielding plate. By a heater installed inside the wafer processing chamber 7, plasma processing is carried out at a high reaction speed without causing damage to a work.