An apparatus for a plasma processing includes an annular member, a support unit, a chamber and a pressure control unit. The annular member has a groove or a protrusion circumferentially formed on a bottom surface thereof, the groove or the protrusion having a first thread circumferentially formed on a side surface. The support unit has a protrusion or a groove circumferentially formed on a placing surface on which the annular member is placed such that the groove or the protrusion of the annular member is fitted with the protrusion or the groove of the support unit, the protrusion or the groove of the support unit having a second thread circumferentially formed on a side surface thereof. The chamber has therein the support unit. Further, the pressure control unit controls a pressure in the chamber such that a driving force for circumferentially rotating the annular member is obtained.