In a plasma processing apparatus having a processing chamber, a sample stage, a sample, a dielectric-composed insulating film and an electrode, the sample stage can be divided into an upper member and a lower member, the upper member including the insulating film and an electrode, the apparatus includes a socket which is deployed inside a through hole of the upper member, and which is electrically connected to the electrode, a pin which is brought into contact with the socket by being inserted into the socket, and a seal member which is attached onto the socket in order to implement a hermetic sealing between the upper-member side and the lower-member side inside the through hole, the upper-member side being continuously linked to the decompressed processing chamber, the lower-member side being continuously linked to the substantially-atmospheric-pressure side which is the outside of the processing chamber.