To prevent the occurrence of unstable breaking by metallic fatigue, by minimizing generation of a crack from a rivet hole, by improving the rivet hole and a countersunk rivet.

Stress concentration is restrained by a method for forming a corner part as a convex surface 6r over the whole periphery for eliminating the corner part such as the rivet hole, to restrain the corner part of a fastening hole from becoming a starting point of causing the crack. The convex surface 6r of the rivet hole can be easily formed by being formed by punching or even by a drill and a rotary polishing unit. A rivet 3 is manufactured by plastic molding by pressing a metallic body in a mold hole of a metal mold by forming the metal mold having the inner periphery in the same shape as the fastening hole of the convex surface 6r. If the crack is caused from the rivet hole, an emergency measure can be performed by guiding the crack to the bypass hole side by opening one or more of crack bypass holes on the opposite side to the shortest passage in a bypass route except for the shortest passage between the mutual adjacent fastening holes.