The present invention provides an igniter for an air bag system which has an excellent operation performance and can be reduced in weight. A capacitor and an integrated circuit are provided in an igniter for an air bag system utilizing bus lines 10 and 11. In the integrated circuit, an impedance converting circuit is provided between the bus lines 10 and 11 and a rectifying circuit, and thereby, a capacitor with a large capacitance (.mu.F order) can be charged with a small load capacitance (pF order).