Curtain airbag installation structure

A curtain airbag (1) is disposed along a roof side rail (2R) of a motor vehicle in the state of being folded into an elongated shape extending in the fore-and-aft direction. A folded body of the curtain airbag (1) is covered by a roof lining (5) attached to the ceiling portion of the vehicle. A space (S) for allowing passage of the curtain airbag (1) in the course of inflation is formed between an end edge (5a) of the roof lining (5) and a cabin side surface (2f) of a roof side rail (2R). The space (S) is closed by a lip portion (10b) projecting toward the cabin from a weather strip (10) attached to the roof side rail (2R). The lip portion (10b) is provided with a deformation inducing portion (recessed groove) (10c) for inducing bending deformation thereof so that the lip portion (10b) leaves the space S as the curtain airbag 1 which is in the course of inflation passes through the space S.