Inflator with improved reliability wherein charge holder 37 that gives directivity to a detonation wave generated due to combustion of priming 36 is provided to igniter 26, thereby promoting rupture of plate 19. Diffuser portion 320 is connected in the opening portion side of housing 312, and gas discharging port 340 is connected to diffuser portion 320. Diffuser portion 520 is connected in the opening portion side of inflator housing 512, and gas discharging port 540 is connected to diffuser portion 520. Outflow directions of the pressurized media within each gas discharging port 340, 540 and each respective axial direction of inflator housings 312, 512 are coincident with each other at actuation.