A curtain airbag device that allows easy recognition and correction of twisting of an airbag during attaching. The curtain airbag device can be stored in a compact manner during transportation. The curtain airbag device including an airbag that is disposed along a roof side rail of a vehicle interior, and that can deploy so as to cover a window portion on a side face of the vehicle interior, the curtain airbag device further including a cover that covers the airbag, at least, in a part of the folded or rolled airbag in the longitudinal direction. The cover is formed of a pliable fabric material of polymer fibers, and maintains the shape of the rolled-up airbag through mutual fusion of at least a part of the polymer fibers. A high stiffness portion harder than other portions and formed during the fusion of the cover is provided in the cover extending in the longitudinal direction of the cover.