To provide a stored gas inflator, capable of injecting gas even with a low output initiator.

This stored gas inflator 1 has a pressure vessel 10. A gas filled chamber 12 is provided inside the vessel 10. A gas jet port 14 at the top end of the vessel 10 is closed by a burst shim 16. A duct 34 for introducing the injected gas pressure of the initiator 30 so as to work from the inside of the filled chamber 12 to the burst shim 16 is mounted at an initiator installation part 32 at the rear end side of the vessel 10. The duct 34 is extended in the filled chamber 12 from the installation part 32, and the top end part faces the burst shim 16. When the initiator 30 is exploded, the injected gas pressure works on the burst shim 16 from the inside of the filled chamber 12 through the duct 34 to apply bursting pressure to the burst shim 16.