Abstract: There is described an instrument capable of immediately and accurately extracting contaminants from solely either side of a wafer surface or from a certain area on the wafer surface. O-rings, each of which is partially cut, are attached to respective sides of wafer holding members. A wafer is held from respective sides by the wafer holding members. Extraction of contaminants from the upper surface of the wafer is carried out independently of extraction of contaminants from the underside of the wafer, by means of feeding extraction solvent to the interior spaces defined by the respective O-rings. Thereby, quick and appropriate extraction of contaminants from either side of a wafer.