To provide a position adjusting device for a vehicle capable of accurately aligning a central axis of the vehicle with a reference line in a short time.

The position adjusting device for the vehicle includes outriggers at front, back, right and left and is formed with an arm and a jack cylinder provided on an end of the arm to move up and down. A tread plate is laid under the outriggers at front, back, right and left, wherein the tread plate includes a tread plate body, a slide plate base fixed on the tread plate body, a jack cylinder holding part having a recessed part in which a tip of the jack cylinder is set, reciprocatably mounted in the slide plate base, and a hook. A chain is extended between the hooks of the adjacent tread plates without any looseness. The jack cylinder holding part is reciprocated in the slide plate base to align the central axis of the vehicle with the reference line.