Hybrid inflator

A hybrid inflator (10) includes: a cylindrical housing (11) having an open end portion, and an interior thereof being adapted to be charged with a pressurized gas; an igniter housing (20) attached to the open end portion, in which ignition means are accommodated; a combustion chamber housing (40) storing a gas generating agent (41) therein and having at least one through hole (45a), the combustion chamber housing being disposed inside the cylindrical housing and connected to the igniter housing; a communication path (26) extending between the igniter housing and the combustion chamber housing; a rupturable plate (50) closing the communication path, the rupturable plate having a circular closing portion (51) which closes the communication path, and a fixing portion (52) formed on a peripheral edge of the closing portion, an outer diameter of the rupturable plate and the inner diameter of the combustion chamber housing (40) being about the same.