GAS GENERATOR

To obtain a gas generator that is easier to manufacture than before. A gas generator has a long substantially columnar outer shape, and includes a housing , a first holder , a second holder , and a third holder attached near one opening end of the housing , an igniter that is held by the second holder and ignites a gas generating agent , a closing member attached to the other end of the housing so as to close the other opening end of the housing , and a filter . The second holder is fixed to the housing by forming a circumferential wall and a circumferential wall in a state where the second holder is sandwiched between the first holder and the third holder . The third holder is fixed to the housing by performing diameter reduction processing (caulking processing or the like) from an outer circumference to an inner side of the housing at a position corresponding to an annular groove portion to form the circumferential wall