To obtain a gas producing agent composition for an air bag using a non azide-based gas having high combustion speed and excellent safety by mixing trihydrazinotriazine as a fuel and an oxygen acid salt or a metal oxide, etc., as an oxidizer.

A gas producing agent composition for an air bag is obtained by mixing trihydrazinotriazine as a fuel and an oxygen acid salt, a metal oxide, a metal double oxide or their mixture as an oxidizer, as essential components. As the oxygen acid salt, ammonium nitrate, sodium nitrate, magnesium nitrate, sodium nitrite, potassium chlorate, etc., is suitable. As the metal oxide, copper oxide, manganese dioxide, etc., is suitable. Furthermore, carboxymethyl cellulose, starch, polyvinyl alcohol, microcrystalline cellulose, molybdenum disulfide, acid clay, talc, bentonite, diatomaceous earth, kaolin, etc., can be contained in the composition as a binder.