PROBLEM TO BE SOLVED: To efficiently remove the foreign matter sticking to member surfaces by injecting high-pressure water in water or water atmosphere to generate cavitation and casting the cavitation air bubbles diffused by a refraction and diffusion plate to wafer surfaces without directly bringing these bubbles colliding to the wafers etc. which are the objects to be washed. SOLUTION: The mechanically polished or chemically polished wafers 401 prior to washing are transferred by a manipulator from storage shelves to a washing tank and are chucked by a polyhedral chuck 402 previously installed in the washing tank. While a table 407 mounted at a chucking device is rotated, the high-pressure water is injected into the water tank from a nozzle 408 for a water jet and is directed toward the cavitation reflection and diffusion plate 403 on the table 407, by which the cavitation air bubbles are generated. The deposits are removed by the microjets or impact waves generated when the cavitation air bubbles diffused on the surfaces of the wafers 401 by the cavitation reflection and diffusion plate 403 collapse at their surfaces and near the surfaces.