The present invention provides a seat frame inflator including a seat frame housing portion formed of a seat frame having a hollow structure and forming an outer shell of a pressurized gas chamber, and a partition member disposed on a hollow side of the seat frame and configured to isolate the pressurized gas chamber and a gas chamber outer region from each other. The partition member is provided with a communication hole, and a closing member configured to close the communication hole. The seat frame inflator includes an opening member disposed on the hollow side of the seat frame, and configured to open the pressurized gas chamber, and a gas discharge port formed in the seat frame to face the gas chamber outer region and configured to discharge, from the gas chamber outer region to the outside, the pressurized gas flowing from the pressurized gas chamber.