PURPOSE: To enable the moving action of a long stroke to be accurately controlled, by parallelly setting a horizontally moving table to a ball thread and fixing a transmission arm to a ball nut screwed to the ball thread.

CONSTITUTION: A horizontally moving table 1 is guided by crossed roller guides 2. A ball thread 3 can be reversibly rotatably driven through gears 6, 7 by a DC servomotor 5. A transmission arm 17 is fixed to a ball nut 16, and the arm 17 places its point end part to be opposed to an upper surface of the horizontally moving table 1. The horizontally moving table 1 fixes onto it a bracket 9 for transmission to be opposed to the transmission arm 17. The table, both positioning a piezostat 10 and mounting a tension spring 11 to be interposed between the transmission arm 17 and the transmission bracket 9, provides a holding pressure to be given for the piezostat 10.