To reliably prevent slipping-out of a connecting pin even when a traveling vehicle receives impact from the outside by reciprocating the connecting pin for mutually connecting mutual vehicles in these lengthwise direction, and prohibiting reciprocating motion of the connecting pin when the connecting pin moves up to a prescribed position.

When a grip 110 is fitted in a prohibiting long hole 102b by being inserted into a guide long hole 102 of a guide plate 100, a connecting pin 50 is positioned on the lowest end to connect a mating vehicle. At this time, both end parts 70a of a guide arm are fitted in a lower end hole 62c of an inclined long hole 62a formed on a side wall of a cylindrical body 60. A disk-shaped member 90 is positioned in the vicinity of an upper plate 42. The grip 110 is energized downward by a coil spring 120. Thus, as long as force for rotating the grip 110 in the peripheral direction of the side wall does not act by upward force stronger than energizing force of the coil spring 120, the grip 110 cannot move to the other position from the prohibiting long hole 102b, so that slipping-out of the connecting pin 50 from a connecting plate can be reliably checked.