To unify the distribution of a film thickness on the whole face of a board by independently and concentrically controlling the working pressure, to automatically equalize the inclination of a board holding face to a grinding face of a grinding tool, and the camber, the waviness or the like of the board itself, to flatten the board with high accuracy, and to easily mount and demount the board.

This board holding device C1 comprises plural fluid chambers 2a, 2b, etc., concentrically defined in a frame body 1 opened at its board holding face side, plural concentric annular pistons 3a, 3b, etc., respectively vertically movable mounted on each of plural fluid chambers 2a, 2b, etc., and a pressurization and decompression controlling means 8 for independently increasing or decreasing the internal pressure in the plural fluid chambers 2a, 2b, etc., for independently moving the annular pistons 3a, 3b, etc., the board W is fitted to an inner peripheral side face 1i of the frame body 1, and held on surfaces of the independently positioned plural annular pistons 3a, 3b, etc., through a backing material 11.