PURPOSE: To obtain an inexpensive inflator filter having small filtration resistance, satisfactory residue collecting property, and less toxic gas generation and easy to handle using a paper ceramic as the material of the inflator filter.

CONSTITUTION: A gas generating agent 10 in a gas generating chamber 9 is decomposed at high temperature by the operation of an ignition system 11 to rapidly generate a combustion gas, which is sent from the upper part toward the lower part in a filter chamber 14 formed by the layers of a metal gauze body 15 through an inner cylinder 7 and upper receiving body 6 forming the gas generating chamber 9. The gas is passed through a gas outflow passage 13 formed by an cylindrical bulkhead 12 and a lower receiving body 5 and further through a filter 1 provided in an opening part 16 on the side wall of a vessel A to filter fine particles, and blown out to rapidly expand an air bag B. In this case, the filter 1 is formed of a ceramic paper 2, the ceramic paper 2 is reinforced by a metal gauze 3, and the organic binder content of the ceramic paper 2 is set less than 5%.