A rear seat airbag module includes: an airbag; and an inflator configured to supply gas for expansion and deployment into the airbag. The rear seat airbag module is attached to a frame of a seat back of a vehicle seat, and is configured to expand and deploy the airbag to a seat rear side of the seat back. The rear seat airbag module is displaceable to the seat rear side or deformable to the seat rear side due to an easily deformable configuration, by being pressed by a back of an occupant seated on the vehicle seat, as a result of the back being sunk in the seat back due to an impact of a rear collision of a vehicle.