To constitute a vehicle-to-vehicle connecting mechanism to enable a combination vehicle travelling on an optional travelling road surface to travel constantly maintaining a stable posture without receiving travelling hindrance.

A horizontal shaft part 24 of the torsional supporting shaft 22 is extended from the one vehicle 12 to between two flexible motion rods 16, 18 to start and control up-and-down movement and left and right oscillation arranged in an upper area seen from the travelling road surface S in the connecting space between the combination vehicles 12, 14 so as to form a torsional tilting axis of the other vehicle 14. A lower area inside the connecting space is made vacant by connecting a vertical shaft part hanging down from an inner end 24a of the horizontal shaft part 24 to the vehicle 14 through a universal joint 20. A torsionally tilting axis at the time of inclined movement is arranged above a vehicle center-of-gravity G2 by constituting it to give a springing property for torsional returning revolution by elastic means 32, 32 against a horizontal shaft part 24 of a torsional supporting shaft 22.