A gas generator, wherein the second cup (12) of an ignitor (4) is fitted closely a first cup (2), a seal member (19) is disposed between the base end (2c) of the first cup (2) and the ignitor (4), and the base end (2c) and the ignitor (4) are fixed by crimping the holder (5) toward the ignitor (4) to tighten together the holder (5) and the ignitor (4).
