The present invention relates to a gas generator for a restraining apparatus of a vehicle including: a housing having a gas discharge port; a gas source; and an ignition device accommodated inside the housing, the ignition device being connected to an outer power source through an opening of the housing, the ignition device including a igniter body which has a conductive pin and is fixed by crimping an igniter collar, the igniter collar having a plug-accommodating chamber for inserting a plug to be connected with the conductive pin, at least part of a wall surface of the plug-accommodating chamber being formed by a holder which is an independent member formed of a non-electroconductive material and is disposed inside the igniter collar, the holder being fixed in a state of contact with the igniter collar and a housing wall surface including a circumferential edge of the opening.