There is provided a plasma processing apparatus capable of stably generating plasma by suppressing oscillation of a plasma potential, and capable of preventing contamination caused by sputtering a facing electrode made of metal. A high frequency bias power is applied to an electrode within a mounting table for mounting a target object thereon. An extended protrusion 60 is formed at an inner peripheral surface of a cover member 27. The extended protrusion 60 is formed toward a plasma generation space S and serves as a facing electrode facing an electrode 7 within a mounting table 5 with the plasma generation space S therebetween. A ratio of a surface area of the facing electrode with respect to that of an electrode for bias (facing electrode surface area/bias electrode area) is in a range of from about 1 to about 5.