a curtain airbag device includes a curtain airbag disposed along an upper side surface of a vehicle facing a cabin in a folded state to be able to expand downwardly along the side surface , and an inflator for inflating the curtain airbag . a guide airbag is arranged to expand substantially at the same time when the curtain airbag is expanded . the guide airbag guides the curtain airbag toward the cabin and / or regulates an expanding direction of the curtain airbag .