It is an object to ensure that, even when knee regions of an occupant are in a near state with respect to a storage section of a knee airbag at the time of a frontal collision of a vehicle, the knee regions can be restrained appropriately by the knee airbag.A knee airbag 14 stored in a folded state in a glove box door 22 (a storage section) receives a supply of a gas at the time of a frontal collision of a vehicle 18 and inflates and deploys toward knee regions 36K of an occupant 36 seated in a front passenger seat 12 (a vehicle seat). At this time, when the knee regions 36K of the occupant 36 are in a near state with respect to the glove box door 22, the gas inside the knee airbag 14 becomes ventable to the outside from a vent hole 16, The vent hole 16 appropriately vents this gas from the inside, of the knee airbag 14, and the reaction force of the knee airbag 14 with respect to the knee regions 36K are reduced.