A polishing apparatus comprises a first polishing table having a first polishing surface, a substrate carrier for holding a substrate and positioning the substrate so as to bring a surface of the substrate into contact with the first polishing surface, a pressing mechanism for pressing, against the first polishing surface, the surface of the substrate which has been brought into contact with the first polishing surface by the substrate carrier, a retainer ring mounted on the substrate carrier so as to surround the substrate which has been pressed against the first polishing surface by the pressing mechanism, and a retainer-ring-position-adjustment mechanism for adjustably positioning the retainer ring relative to the substrate, which has been pressed against the first polishing surface, in directions toward and away from the first polishing surface.