To improve the assemblability of a cylindrical member to an inflator with a bolt with a simple constitution.

This inflator 20 is the inflator with the bolt integrally having a fixing bolt 44 fixed to a casing 18. A sleeve 40 also has a tongue piece part 40b extending along the longitudinal direction of the inflator 20. This tongue piece part 40b is formed with an insertion hole 48 having a long hole part 48a formed in a long hole shape along the longitudinal direction of the inflator 20 and a short hole part 48b formed to become a substantially right angle to this long hole part 48a.