Abstract: A coupling device for connecting a male member and a female member comprises a lock pin resiliently urged toward the male member by means of a spring to permit an insertion of the female member but extend into a lock groove of said male member to connect these members, an outer race rotatively resiliently urged in one direction relative to the female member and formed with a recess for receiving a part of the lock pin to permit it to remove from the lock groove of the male member, a slide pin for locking the outer race relative to the female member when the male member is not in the female member and releasing the outer race relative to the female member when the male member is inserted in the female member, and an outer race lock pin urged by an outer race lock pin spring to lock the outer race relative to the female member when the outer race is rotated.