Provided are a wafer polishing method in which, in single side polishing, covering a wafer holding surface (one side surface) with a protective film, a wafer polishing surface (the other side surface) is polished, so that the wafer holding surface can be prevented from being etched and contaminated by a polishing agent; a wafer cleaning method in which the protective film that remains behind on the wafer holding surface after polishing can be efficiently removed, and a waste cleaning solution is easily treated; and a wafer protective film that sufficiently covers the wafer holding surface in polishing but is effectively removed in cleaning. In a wafer polishing method in which a wafer holding surface of one side surface of a wafer is held and a wafer polishing surface of the other side surface thereof is polished while dripping a polishing agent, the wafer polishing surface is polished while covering the wafer holding surface with a synthetic resin protective film of etching resistance against the polishing agent, good adhesiveness to the wafer and a property easy to peel off from the wafer after polishing.