A polishing apparatus is used for polishing a surface of a substrate such as a semiconductor wafer to planarize the surface of the substrate. The polishing apparatus includes a polishing table having a polishing surface, and a top ring configured to hold a substrate with an outer circumferential edge of the substrate surrounded by a retainer ring and to press the substrate against the polishing surface. The top ring is movable between a polishing position above the polishing table, a position laterally of the polishing table, and a cleaning position. The polishing apparatus includes a cleaning unit disposed in the cleaning position and configured to eject a cleaning liquid toward the lower surface of the top ring, which is being rotated, thereby cleaning the substrate held by the top ring together with the lower surface of the top ring.