A guide pin piercing jig includes a cylinder unit and a frame having a positioning projection at a tip thereof, in which the cylinder unit has plural parallel guide pin insertion cylinders and tentative fixing unit and is attached to the frame slidably so as to be directed to the tip of the frame. It becomes possible to pierce living body bone with plural guide pins for hollow drills to a proper portion of a living body bone in a proper direction with parallel arrangement to form a bone tunnel that has a rectangular or elliptical opening and is suitable for tendon transplantation.