To reduce the electric energy to be input to an igniter and to set a power conservation type by forming the igniter of ammonium nitrate, high melting point-metal wire or aluminum fuse.

An igniter 15 is made of a combination of arrononium nitrate water 13a and high melting point metal wire 14a (or aluminum fuse 14). A voltage is applied between a cathode plate 7 and an anode plate 11, and when a current is supplied to the wire 14a, the wire 14a is melted to generate plasma by Joule heat, and thermochemical reaction occurs with the water 13a. The high-temperature and high-pressure gas generated in this manner destroys the cathode 7 to flow to a main reacting part 8, which is explosively reacted by the thermal energy of the gas. Accordingly, the input electric energy can be reduced as compared with that of prior art to make it possible to perform the reduction of a power source shape.