An igniter assembly includes, an igniter body having an ignition portion and an electroconductive pin, a substantially cylindrical collar surrounding and retaining the igniter body, and a tubular holder disposed inside the collar and surrounding the electroconductive pin to connect the electroconductive pin to a connector. The igniter body, the collar, and the tubular holder are separate members, and are integrated by a resin (provided that the holder is not fitted by being inserted into the collar or a resin portion covering the collar). The tubular holder has a tubular body portion and a convex portion covered by the resin and formed on an outer circumferential surface of the tubular body portion in the diametrical direction or on an inner circumferential surface of the tubular body portion in the diametrical direction. A fitting portion is provided to the inner circumferential surface of the tubular body portion for fitting the connector.