The head-protecting airbag apparatus includes an airbag folded up in an elongative contour for covering a window of vehicle upon deployment, and a plurality of cases arranged along the length direction of the folded-up airbag for housing the airbag. The airbag apparatus is mounted on the vehicle by attaching mounting portions of the airbag along an upper periphery of the window together with the cases. The cases are connected by a bendable connecting member and thereby permitting the airbag stored in the cases to be transported in a bent state at the connecting member. The connecting member announces the occurrence of twisting of the airbag between the cases by shortening the distance between the cases for preventing the airbag from being mounted on the vehicle in a twisted state when the airbag apparatus is unfolded for mounting on the vehicle.