A polishing apparatus makes it possible to polish and remove an extra conductive film while preventing the occurrence of erosion and without lowering of the throughput. The polishing apparatus includes: a polishing table having a polishing surface; a top ring for holding a workpiece having a surface conductive film, and pressing the conductive film against the polishing surface to polish the conductive film; an optical sensor for monitoring the polishing state of the conductive film by emitting light toward the conductive film of the workpiece held by the top ring, receiving reflected light from the conductive film, and measuring a change in the reflectance of the reflected light; and a control section for controlling a pressure at which the workpiece is pressed on the polishing surface.