An inflator (1) comprised of an inner case (19) and an outer case (28). The inflator (1) includes a combustion chamber located inside the inner case (19), a plurality of gas discharge ports (16) formed on the outer case (28), a gas outlet port (11) formed on an outer surface of the inner case (19) and a gas guide section that guides the inflation gas exited the gas outlet port (11) toward the gas discharge ports (16). The gas guide section includes between the outer case (28) and inner case (19) a guide wall (13a) provided with a guide plane that contacts with and redirects the inflation gas. The guide plane is formed into an arc face so as to swivel the inflation gas exited the gas outlet port (11) in a swirl or helical fashion, guide the inflation gas toward the gas discharge ports (16) and capture residuals.