To increase combining force at a caulked part and reduce an extension.

A first recessed part 16 facing from a first member 10 side to a second member 12 side is formed in a caulked part 14, and a second recessed part 18 facing from the second member 12 side to the first member 10 side is formed therein. A junction surface 20 between the outer peripheral surfaces of the first recessed part 16 and the second recessed part 18 is formed generally in S-shape in cross section. The bent part 20A of the junction surface 20 on the first recessed part 16 side is positioned on the first member 10 side of a general junction surface 22, and projected to the inside of the first recessed part 16 (in the direction of arrow A in Fig. 1). A bent part 20B on the second member 12 side is positioned on the second member 12 side of a bottom part junction surface 24, and projected to the outside of the second recessed part 18 (in the direction of arrow B in Fig. 1).