A polishing apparatus has a turntable with an abrasive cloth mounted on an upper surface thereof and a top ring disposed above the turntable for supporting a workpiece to be polished against the abrasive cloth under predetermined pressure. The turntable is rotatable by a first motor through a timing pulley connected to the first motor, and the top ring is rotatable by a second motor through a timing pulley connected to the second motor. A torque detector incorporated in the timing pulley connected to at least one of the first motor and the second motor detects an output torque produced by the at least one of the first motor and the second motor.
