A polishing table holds a polishing pad. A top ring holds a semiconductor wafer. A swing arm holds the top ring. The swing arm swings around a swing center on the swing arm during polishing. An optical sensor is disposed on the polishing table and measures an optical characteristic changeable in accordance with a variation in film thickness of the semiconductor wafer. A fluid supply control apparatus determines a distance from an axis of rotation to the optical sensor when the semiconductor wafer is rotated by the top ring. An end point detection section detects a polishing end point indicating an end of polishing based on the optical characteristic measured by the optical sensor and the determined distance.