A polishing apparatus in which a liquid containing a slurry hardly enters into a gap between a top ring body and a retainer ring during polishing, and the slurry can be discharged by cleaning even if the liquid containing the slurry enters into the gap, and slurry particles can be prevented from being attached to a surface of a substrate (wafer) when the substrate (wafer) is released is disclosed. The polishing apparatus includes a top ring having a top ring body and a retainer ring provided at an outer circumferential portion of the top ring body, and configured to hold a substrate to be polished and to press the substrate against the polishing surface, and a cleaning mechanism provided at a substrate transfer position for transferring the substrate to the top ring or receiving the substrate from the top ring, and having a cleaning nozzle configured to eject a cleaning liquid toward the top ring. The retainer ring has a recess formed over an entire circumference of an inner circumferential surface of the retainer ring. The cleaning nozzle is configured to eject the cleaning liquid toward the recess of the retainer ring.