A head protection airbag device includes an airbag including a front seat protection portion, and an end side expansion portion, and a partition closing portion. The airbag is configured to be provided with a single receiving area where the head which moves diagonally forward at the time of an oblique collision or an offset collision of the vehicle is received by the front seat protection portion, and a collaborative receiving area where the head is received by the front seat protection portion and the end side expansion portion. The partition closing portion is linearly provided to be inclined forward and downward in a state where the airbag is viewed from a side when the expansion of the airbag is completed. The collaborative receiving area includes vehicle inner side surfaces of the end side expansion portion and the front seat protection portion with the partition closing portion interposed therebetween.