PURPOSE: To easily align the center of a rotary table and the tool center with each other, and easily perform correction to thermal deformation.

CONSTITUTION: A taper-shaped give 21 is movably inserted into a slidingly movable surface between one end part of a cross rail 4 striding over a rotary table 1 and a guide rail 3, and a driving motor 22 to move the give 21 is arranged on the cross rail 4, and the taper-shaped give 21 is moved on the slidingly movable surface between the guide rail 3 and the cross rail 4 by the driving motor 22. The cross rail 4 is longitudinally moved by a microscopic distance to a column 2, and a center position of a ram 6 is longitudinally moved to a rotational center position of the rotary table 1, and the central position of the ram 6 and the rotational center position of the rotary table 1 are corrected, and the center of the rotary table 1 and the tool center are easily aligned with each other.