A plasma processing apparatus includes a processing chamber in which a wafer 1 is processed by using plasma, a radio-frequency power supply that supplies radio-frequency power for generating the plasma, a sample table 2 which is arranged in the processing chamber and in which the wafer 1 is mounted, and a DC power supply 106 which is electrically connected to the sample table 2 and which causes the sample table 2 to generate a suction force. The sample table 2 includes a protruded portion 201a that sucks the wafer 1 by the suction force and a level different portion 201b protruding from a lower portion of the protruded portion 201a. A ring 5 that can be in contact with a lower surface of the wafer 1 is provided outside the protruded portion 201a. A space portion 7 formed by the wafer 1, the protruded portion 201a, and the ring 5 is sealed in a state in which the wafer 1 is sucked to an upper surface of the protruded portion 201a of the sample table 2.