PURPOSE: To prevent transmission of vibration from a field forming member to a mover and to prevent deterioration of travel performance of mover by supporting the mover not through the field forming member but directly on the base.

CONSTITUTION: Upon driving of first and second movable bodies 10a, 10b, bearings 11a, 11b move along a shaft 3 and rollers 12a, 12b roll on a rail 4 and thereby the first and second movable bodies 10a, 10b travel in the directions A and B. At the same time, the frame body C is subjected to reaction and a bearing 35 moves along a shaft C while furthermore a roller 36 supporting a field forming member rotates to move the frame body C in reverse direction. Since the shaft 3 and the rail 4 supporting the first and second movable bodies 10a, 10b are fixed on a base frame 1, vibration or positional shift due to movement of the frame body C does not effect adversely on the travel of the first and second movable bodies 10a, 10b.