The utility model relates to a gas generator. A body is provided with an ignition chamber, a combustion chamber and a filtering chamberbody, a gas generating composition is put in the combustion chamber; an electric squib, a fixing device and an ignition drug are arranged in the ignition chamber. The utility model is characterized in that the body comprises an upper casing body and a lower casing body, and the lower end surface of the upper casing body and the upper end surface of the lower casing body perform a oppositely rotating and friction welding to form an endless belt-shaped welding seam; and the filtering chamber comprises the outer wall of a filter screen and the inner circular ring of the upper casing body. The utility model resolves the deficiencies that the prior art needs casing body distortion to form an air duct, and has a higher requirement to the generator casing body intensity and the part size in the casing body, and the distortion is larger when the generator works, and the utility model has the advantages that the primary pressure establishing is fast, the inner pressure in the ignition chamber is low, the outlet pressure is repeated and steady, the filtering is good, the dust is less, the outlet temperature is low, and the utility model is suitable for all gas generating composition.