PURPOSE: To facilitate correction of deformation of precision member due to processing error and thermal distortion, by making pressure-applying control of fluid body filled in a pressure chamber formed in a precision member.

CONSTITUTION: Pressure chambers 2aW2d are formed by excavation of inside of a member 1, and the pressure chambers 2aW2d are charged with fluid bodies 3aW3d. The pressure chambers 2aW2d are provided with pressure-applying screws 4aW4d with hinges, and pressure-applying control of the fluid bodies is conducted. In case when a bend is caused to a precision member 1 constituting a reference surface and a slide surface, etc. of a mechanical device due to heat-treatment, correction of the bend is made in such a manner as to screw in the screw 4b inside the precision member 1 to raise pressure of the fluid bodies in the pressure chamber 2b, reverse the screw 4d on the opposite side to reduce pressure of the fluid bodies in the pressure chamber 2d and control outside dimensions of the member 1.