PURPOSE: To polish a semiconductor wafer to high flatness by rotating a hard plate while uniformly pressing the whole face thereof from its back face via a rigid press plate.

CONSTITUTION: A fluid is fed under pressure into a cylinder 14 to press a press plate 11 of a rigid material via a piston 13, and the whole face of a glass plate 3 is uniformly pressed from its back face via a cushion sheet 12. Thereby, a semiconductor wafer 4 which is bonded to the glass plate 3 is uniformly pressed against a surface plate 1. In this condition, the press plate 11 is rotated via a shaft 8 sliding the semiconductor wafer 4 on the surface of the surface plate 1 to polish the semiconductor wafer by means of the abrasive cloth 2 of the surface plate 1 at a high flatness.