A curtain airbag housed in an upper part of a side surface portion in a vehicle interior and inflating and deploying along the side surface portion. The curtain airbag includes an end chamber at a front end portion of the curtain airbag that inflates when receiving an inflation and deployment gas. A strap is attached, at a leading end portion thereof, to a first attachment point P on a front pillar 114 of the vehicle and passes through an exterior side of the end chamber, and moreover attached, at a rear end portion thereof, to a seam portion 144 that defines the end chamber. The first attachment portion is set to include a second plane L2 that is vertically below, but parallel to a first plane L1 passing through an A1 break point that is a center of an impact expected area E overlapped with the end chamber.