GAS GENERATOR

A cylinder-shaped gas generator (1A) includes a housing having a first housing member (10) having an elongated cylindrical shape with a bottom, an igniter (30), a partition plate (40), a dividing member (50), an enhancer agent (61), a gas generating agent (62), and a filter (70). The dividing member (50) is made of a cylindrical member with a bottom that is located in a working gas generation chamber and includes a cylindrical portion (52), a bottom portion (53), a first communication hole (54), and a hollow portion (55). The gas generating agent (62) is stored in a portion of the working gas generation chamber excluding the hollow portion (55). Assuming that the outer diameter of the first housing member (10) is set at R1, the diameter of the working gas generation chamber is set at R2, the distance between the bottom portion (53) and the edge, on the bottom portion (53) side, of one of the first communication holes (54) located closest to the bottom portion (53) is set at L1 and the distance between the bottom portion (53) and the end of the working gas generation chamber on the igniter (30) side is set at L2, the conditions of 15 mm ¤ R1 ¤ 22 mm, L1 ¤ 10 mm and 0.026 ¤ L2/R2 ¤ 0.71 are satisfied.