A head protection airbag device includes: an airbag formed so as to cover a window of a vehicle; and a case for storing a folded body of the airbag. The airbag has an engaging hole through which an engaging protrusion passes. The case includes the engaging protrusion. A portion constituting a peripheral edge of the engaging hole has recessed sections recessed from an upper edge of the airbag in front of and behind the engaging hole so as to have a tab-shaped portion. In a state in which the airbag is flatly developed, an upper edge of the tab-shaped portion that has the engaging hole is disposed nearly on a same line as an upper edge of a general section of the airbag which is adjacent to the tab-shaped portion.