PURPOSE: To make a rotary driving body detachable from a guide member, by mounting detachably the rotary driving body supported on a moving frame from the guide member and mounting a means with which the rotary driving body is detached and pressed automatically from and onto the guide member.

CONSTITUTION: A guide rail 17 is installed between driving roller 69 and driven roller 77 and an X-axis motor 15 is driven to rotate the roller 69 and then, a driving guide member 13 is guided by the rail 17 to be displaced in the direction of the X-axis. Further, upon operation of an air cylinder 97, a plunger 101 presses a displacing body and then, a roller 77 is pressed against the rail 17 with a constant force and it is rotated in the opposite direction with respect to the roller 69. Namely, as a supporting body 53 which support the roller 69 and a swinging body 79 which supports the roller 77 are kept constantly energized with a releasing spring 95, the rollers 69 and 77 are rotated under a constant pressing force exerted onto the rail 17. In this case, with the aid of the spring 95, one-touch manual operation becomes available by switching to the manual operation without driving the X-axis motor 15.