A plasma processing apparatus includes a vacuum chamber having a structure that surrounds a space where plasma is generated, a sample stage disposed in the chamber on which a sample to be processed is placed and coil antenna providing an electric field to the space. The structure has a non-conductive member surrounding the space and a conductive member covering the non-conductive member, both of which are disposed between the antenna and the space. The conductive member is electrically floated at least when the plasma is generated.