PURPOSE: To make any movement of a robot at very high speed and in a way of simple control even if inertia force differs at each robot by rotating a screw shaft, moving two robots as a whole, while producing a difference in travel between these robots with rotation of a nut being screwed in the screw shaft.

CONSTITUTION: A common screw shaft 44 extending along a guide rail 42 is rotated by a servomotor 74, two robots 16, 17 are moved along the guide rail 42 as a whole. At this time, when intending to make a difference in travel between these robots 16, 17, a nut 45 being screwed in the screw shaft 44 is rotated as much as a portion for this difference, thereby producing the difference in the travel between the robots 16 and 17.