An improved artificial insemination device with an inner catheter for animals is disclosed. The device is characterized by having a thin flexible tube and a positioning stop member installed respectively at the front end and rear end of an inner catheter that is movably inserted in the catheter tube. The thin flexible tube instantly extends forward from the front end of inner catheter when semen is squeezed into the inner catheter. Thus after the nozzle of catheter tube reaches the first cervical ring of the animal, the inner catheter only needs to extend inward a proper distance, and the semen, with the aid of squeeze force and the thin flexible tube advancing freely along the cervical tract, could be delivered to uterus smoothly, swiftly and accurately without causing trauma to the uterus. Also with the arrangement of the positioning stop member, the distance the inner catheter travels inward can be set. As the depth and location of inward extension are under proper control, the practice of artificial insemination is made simple, convenient, fast, efficient and safe for the animal.