A graduated guide pin for selecting a screw for connecting a fractured bone is formed by a pin-like main body 11 of a radiotransparent metal and ring-like members 12 of a radioopaque metal. The ring-like members are arranged on an outer surface of the main body such that successive members are separated from each other by a distance equal to that of the ring-like members. On an X-ray image, by counting the number of dark portions corresponding to the ring-like members, a length of the fractured bone is measured, and a screw 20 having a suitable length is selected.
