The present invention is provided to prevent yield reduction of semiconductor device in dry cleaning of semiconductor device manufacturing process. The electric action and chemical action due to plasma of a first gas generated by means of a plasma generating means and the physical action due to viscous friction force of high speed gas flow generated by means of a planar pad that is brought close to the main surface of a wafer are applied together for cleaning the main surface of the wafer. After cleaning, the wafer is exposed to plasma of a second gas in the same vacuum chamber and then transferred to the atmosphere.