To inflate an airbag of a protective bag device for a pedestrian and the like as uniformly as possible and to relax the heat resisting property required for the airbag, a gas-generator storage chamber of the airbag is provided at the lower surface thereof. The gas-generator storage chamber houses most of a gas generator. A gas guide member is disposed to surround gas jet ports at the end of the gas generator. Outlets of the gas guide member are arranged above a seaming section in the airbag. In one form, an entry of the gas guide member and an opening of the airbag are firmly bound to the gas generator with a band.