The application discloses a bone screw and a bone connecting device. The bone screw comprises a rod body, a
tail part and a first external thread. The
tail part is connected with the end of the rod body, and the
tail part is provided with a
cutting edge. The surface of the tail part is also provided with a second external thread. The second external thread comprises a first end and a second end. The first end is located on the side away from the rod body of the second end. The outer
diameter of the first end is smaller than the bottom
diameter of the first external thread. The outer
diameter of the second end is larger than the bottom diameter of the first external thread. The second external thread gradually increases in the direction from the first end to the second end. In the application, a part of the second external thread can be pre-installed in the nail hole of the bone, and the thread tapping is
cut from the inner wall of the nail hole of the bone, so that the surgeon can screw the bone screw into the nail hole of the bone.