GAS GENERATOR

A gas generator includes, an ignition device chamber arranged on a first end side of a cylindrical housing and closed by an ignition device including an igniter, a diffuser including a gas discharge port and closing a second end side of the cylindrical housing opposite to the first end in an axial direction, a compressed gas containing chamber disposed between the diffuser and the ignition device chamber and containing therein a compressed gas as a gas source, a first rupturable plate disposed closing off the ignition device chamber and the compressed gas containing chamber from one another, and a second rupturable plate disposed closing off the compressed gas containing chamber and the diffuser from one another, a cup-shaped deflector disposed on a side of the second rupturable plate where the compressed gas containing chamber is disposed, the cup-shaped deflector including a gas passage in a peripheral surface section thereof and a fragile section on at least one of a bottom surface section thereof and the peripheral surface section, and being disposed with the bottom surface section located on a side where the first rupturable plate is disposed, with an opening covering the second rupturable plate, and with a cylindrical gap defined between the peripheral surface section and an inner peripheral wall surface of the cylindrical housing.