PURPOSE: To provide the forward and backward moving device with simple configuration which can be used for every kind of positioning device, for example, the rack welding positioning jig device or the other general machine, etc., and which can moves plural numbers of forward and backward moving stand to the arbitrary position with the common feed screw.

CONSTITUTION: Two feeding screws 14, 15 to be driven in the reverse direction are provided in parallel to a straight advancing guide 12 provided freely advancing and retiring an advancing and retiring stand 10. Two pieces of ring like clutch members 16, 17 are attached freely rotationably on the advancing and retiring stand 10, and nuts 18, 19 to be screwed on each feed screw 14, 15 are provided on these clutch members 16, 17. Respective engaging recessing parts 20 are provided to each clutch member 16, 18. Two numbers of clutch engaging on-off devices 22, 23 to stop the rotation of clutch members by engaging an engaging pin 21 to the engaging recessing part 20 are provided on the advancing and retiring stand 10.