INFLATOR

The present invention provides an inflator which has a sufficient operation performance and secures an operation reliability and operation safety and is manufactured easily. There is provided an inflator provided with a first passage for guiding activation energy of an igniter and a second passage for guiding a pressurized medium to a gas discharging port defined inside and outside two retainers having a cylindrical peripheral wall portion, in which the ruptureble plate sealing the pressurized medium space is held by two retainers disposed axially adjacent to each other.