To prevent center run-out of a lower surface plate, an upper surface plate and a suspending mechanism and to provide stable polishing accuracy.

In an inner plate 38 of the suspending mechanism for suspending the upper surface plate, a pair of driver hooks 59 and 59 and three guide rollers 66, 74 and 74 are provided at a peripheral edge part of a hole 39 provided at the center part. The pair of driver hooks 59 and 59 are provided at opposite positions with the center of the hole 39 as a center. The guide rollers 66, 74 and 74 are provided at three portions at intervals of 120° at the peripheral edge part of the hole 39. When the upper surface plate is lowered, the driver hook 59 is engaged to a groove 9 for driver hook of a driver 8 and the guide rollers 66, 74, 74 are engaged to a groove 10 for guide roller of the driver 8. Center run-out of the driver 8 is suppressed by the three guide rollers 66, 74 and 74 and center run-out of the upper surface plate is suppressed.