A plasma processing apparatus capable of, over a prolonged period of time, controlling a decrease in the value of a DC current flowing within an accommodating compartment. The plasma processing apparatus comprises an accommodating compartment adapted to accommodate a substrate and perform a plasma treatment thereon, a high-frequency power source adapted to supply high-frequency power to the inside of the accommodating compartment; a DC electrode adapted to apply a DC voltage to the inside of the accommodating compartment, a ground electrode provided within the accommodating compartment and used for the applied DC voltage, and an exhaust unit adapted to evacuate the inside of the accommodating compartment. The plasma processing apparatus further comprises a shielding member disposed in theaccommodating compartment so as to extend along the flow of exhaust gas, interpose between the flow of exhaust gas and the ground electrode, and form a cross-sectionally elongated groove-shaped spacebetween the shielding member and the ground electrode.