Gas generator (1) comprising, in a cylinder housing (10), a
combustion chamber (20) filled with gas generating means (25, 26) as a gas source, and a gas outlet opening (16) for expelling a gas generated by the
combustion of the gas generating means (25, 26), wherein the
combustion chamber (20) contains an ignition device containing an igniter (11) and closing a first end opening (10a) of the cylinder housing (10), a partition wall (15) closing a second end opening (10b) on the side axially opposite the first end opening (10a), and a perforated cylinder body (21) arranged in the
combustion chamber (20); wherein the igniter (11) comprises an igniter main body having an ignition portion (12) and an igniter collar (13) surrounding and holding the igniter main body; wherein the perforated cylinder body (21) is arranged such that its first end (21a) surrounds the ignition section (12) of the igniter (11) and its second end (21b) is arranged on the axially opposite side on the side of the partition wall (15); wherein an interior of the perforated cylinder body (21) is a first chamber (22) filled with a portion of the gas generating means (25), and an exterior of the perforated cylinder body (21) is a second chamber (23) filled with the remaining gas generating means (26); and at least one gas outlet opening (16) is a through hole formed in a section of the partition wall (15) facing the second chamber (23), and no gas outlet opening is formed in a region of a length of more than 0.3 from the surface of the partition wall (15) on the
combustion chamber (20) side toward the first end opening (10a) in a portion of the cylinder housing (10) facing the second chamber (23) when a length from the first end opening (10a) of the cylinder housing (10) to the surface, on the
combustion chamber (20) side, of the partition wall (15) closing the second end opening (10b) is set to 1, wherein the second end (21b) abuts against a surface (15a) of the partition wall (15) on the combustion chamber (20) side or is provided opposite thereto with a small gap therebetween, the small gap being a gap equal to or smaller than a
diameter of holes of the perforated cylinder body (21).