A gas generator (1A) is provided with: a lower shell (10) as a housing; an igniter (40) which includes a squib cup (44) and a closing plug (43); and an affixation section (30) which is formed from a resin formed body and which affixes the igniter (40) to the lower shell (10). The squib cup (44) includes: a contact section (A) which is in contact with the closing plug (43); and a non-contact section (B) which is not in contact with the closing plug (43). The affixation section (30) includes a cover section (35) which is secured to the outer peripheral surface of the squib cup (44). The cover section (35) has: a lower annular cover section (36) which covers a part of the contact section (A); and an upper annular cover section (37) which covers a part of the non-contact section (B). The thickness (t2) of the upper annular cover section (37) is less than the thickness (t1) of the lower annular cover section (36). The cover section (35) is formed in a stepped shape having a substantially flat and annular step forming surface (38) perpendicular to the axial direction of the squib cup (44).
