To provide a driving coupling device capable of transmitting motive power from a motor of an engine, etc., by torque in the case when an output shaft positively rotates and easily changing generated torque in accordance with specifications as torque does not transmit in the case when it reversely rotates.

It is constituted of an output shaft 2a directly connected to a cam ring 2 inserted into a ring recessed part 1a of a main body 1 free to rotate, supported by a bearing 3 and projected, an input shaft 5a directly connected to a rotor 5 inserted into a ring hole 2b of the cam ring 2 free to rotate, supported by a bearing 11 and projected from a plate 6 and a side plate 8 to be sealed, vanes to be fitted and inserted into a plural number of grooves roughly equally molded in the radial direction of the rotor 5 free to rise and set, ports (a), (b) provided on the side plate 8 communicated to an oil chest formed of the vanes, the rotor 5, a recessed part of the cam ring 2 and the plate 6, a relief valve 14 arranged on a conduit run 13a and a check valve 15 arranged to allow a flow only to the port (a) from a tank T.