In one form, a curtain airbag device is provided having a gas introduction portion that is folded so as to be disposed on a side surface of a folded body of a curtain airbag main body on a roof side portion side. When the vehicle is involved in a side collision or an overturn, an inflator discharges a gas, which is supplied to a curtain airbag, thereby causing the curtain airbag to start to be inflated. In this case, the gas from the inflator initially flows into the gas introduction portion so as to inflate the gas introduction portion. Thus, the inflating force of the folded body of the curtain airbag main body and the inflating pressure of the gas introduction portion are superposed each other so as to press a lower edge of a roof side garnish toward the inside of the vehicle cabin.