To apply a uniform polishing pressure to the whole surface area of a semiconductor wafer and to control the polishing pressure easily.

This surface plate 10 is furnished with a vessel 14 filled with liquid paraffin 24, and the vessel 14 is sealed with an elastic sheet 26, onto which an abrasive cloth 28 is affixed. An air bag 30 is immersed in the liquid paraffin 24. Accordingly it is possible to control the internal pressure of the paraffin 24 only by adjusting the internal pressure of the air bag 30, and to control the pressure applied to the sheet 26 and cloth 28, i.e., the polishing pressure. The paraffin 24 is heated by a heater 32. At replacing the cloth 28, the heating is interrupted so as to solidify the paraffin 24, the vessel 14 is removed, and the cloth 28 is replaced with a new one.