Patent ID: 8152594

Claim:
A polishing apparatus comprising: a polishing table having a polishing surface; a top ring configured to hold and press a substrate against said polishing surface; a top ring shaft configured to lift and lower said top ring; a lifting and lowering mechanism configured to lift and lower said top ring shaft; an elongation detecting device configured to detect an elongation of said top ring shaft; and a controller configured to set a vertical position of said top ring at a time of polishing, and control said lifting and lowering mechanism to lower said top ring to a preset polishing position as the set vertical position, wherein said elongation detecting device comprises: a temperature sensor for measuring a temperature of said top ring shaft; and a calculating device configured to calculate the elongation of said top ring shaft from a change in the temperature measured by said temperature sensor, and wherein said controller corrects the preset polishing position based on the elongation of said top ring shaft which has been detected by said elongation detecting device.