To temporarily assemble (fix) a head protective airbag body to a body inner plate by a mounting bracket of a single kind even when a predetermined part (for example, a part corresponding to a pillar arrangement part) of the head protective airbag body in a folded condition to the body inner plate in a largely twisted manner with respect to other parts.

The head protective airbag body 11 in a folded condition in a substantially square section, is assembled with the body inner plate 21a by using a plurality of mounting brackets 17 (comprising a supporting part 17a of substantially square section having a thin-walled part which can surround the airbag body 11 and can be broken when the airbag body 11 is inflated and developed, a pair of fitting pieces 17b and 17c which are jointly tightened together with a fitting part 11g of the airbag body 11, and a locking part 17d integrated with the fitting piece 17c and fitted to the body inner plate 21).