PURPOSE: To generate no polishing defect at polishing completion time by feeding water to a substrate working part at polishing completion time and ascending the holder for substrate from a polishing vessel face after replacing the substrate surface by water.

CONSTITUTION: An etchant layer in a microthickness is formed on a rotating polishing vessel 5 by feeding an etchant by opening the valve 14 of the etchant and polishing is executed by floating a semiconductor substrate 1 on the etchant layer. After polishing for specified time, the valve 15 of water is opened, the valve 14 of the etchant is closed and the etchant on the polishing vessel 5 face is quickly replaced with water. Polishing is completed by ascending the semiconductor substrate 1 held on a holder 2 from the polishing vessel 5 face after the etchant acting on this substrate 1 being completely replaced with water.