PURPOSE: To prevent vibration and play generated in a condition where a difference in rotating speed between front and rear wheels is small.

CONSTITUTION: In this driving connecting device, a vane pump is constituted by containing a rotor 2 having a vane in a casing 7, and torque is transmitted between front and rear wheels through oil pressure generated according to a difference in rotating speed between the rotor 2 and the casing 7. Friction members 21 housed in a through hole 20 of the rotor 2 are slidingly contacted with side plates 7 and 8 by a compression coil spring 22, and friction torque is generated. That connection between front and rear wheels becomes loose in a condition where a difference in rotating speed is small is prevented by the friction torque.