An airbag device for pedestrian protection to mount on a vicinity of the rear end of a vehicle hood. The airbag includes a transverse inflatable portion that covers a cowl of the vehicle generally entirely in the vehicle width direction when deployed, and an inlet port in a front end region of the transverse inflatable portion to couple with an inflator. The airbag is stored folded-up in a housing. The airbag is folded up through a front-rear contracting step that provides a front-rear contracted bag, i.e. the airbag which has gone through the front-rear contracting step, and a transversely contracting step which folds the front-rear contracted bag with a crease at a vicinity of an outer end in a left and right direction of the inlet port. A transversely-contracted fold portion formed in the transversely contracting step and the inlet port are arranged in a stratified fashion.