An airbag for head-protecting airbag device according to the present invention is normally folded and housed in an upper edge of windows including a front pillar. The airbag includes a gas admissive portion. An inflatable shielding portion of the gas admissive portion includes a plurality of protection portions, at least one of which located toward front end of the airbag acts as front protection portion, and remaining protection portions located rearward of the front protection portion act as rear protection portions. The front protection portion includes a plurality of vertical chambers juxtaposed along the front-rear direction of the vehicle, and each of the vertical chambers is arranged vertically. The rear protection portions include a plurality of horizontal chambers juxtaposed in the vertical direction, and each of the horizontal chambers is arranged along the front-rear direction of the vehicle.