A polishing apparatus is used for polishing a workpiece such as a semiconductor wafer to a flat mirror finish. The polishing apparatus includes a turntable having a polishing surface thereon, a top ring, for holding a workpiece to be polished and pressing the workpiece against the polishing surface, which is movable between a polishing position inside of the turntable and a standby position outside of the turntable, and a first device for keeping at least a lower surface of the top ring wet while the top ring is in the standby position. The polishing apparatus further includes a dressing tool for dressing the polishing surface on the turntable, and a second device for keeping at least a lower surface of the dressing tool wet while the dressing tool is in a standby position.