To connect a belt connecting member (4) of a first member (1) with a snap hook (5) of a second member (2), a neck portion (21) having a circular cross section is provided so as to project from a connecting portion of the snap hook (5), a bulging portion (22) is provided on a tip end of the neck portion (21) so as to radially bulge to define an engaging portion (23), a fitting hole (13) is provided on a connecting portion of the belt connecting member (4) with an engaged portion (15) that is engageable with the bulging portion (22), the engaged portion (15) and the engaging portion (23) are formed in an oval shape having a long axis (L, L′) in a flush plane of the belt connecting member (4) and the snap hook (5) and a short axis (S, S′) in orthogonal planes of the belt connecting member (4) and the snap hook (5), and the engaging force can be largest when the snap hook (5) is in its most general state in use where the belt connecting member (4) and the snap hook (5) are orthogonal.