a method of polishing which includes rotatably supporting a workpiece , positioning polishing plates in such a manner that flat surfaces of the polishing plates oppose one another and are in contact with a surface of the workpiece , and polishing the workpiece by rotating the workpiece around a central axis thereof by use of a workpiece rotator . the method also includes reciprocating the polishing plates on the surface of the workpiece in a radial direction of the workpiece while pressing the workpiece between the flat surfaces of the polishing plates .