A gas generator comprising: an elongated cylindrical housing containing a combustion chamber in which a gas generating agent is arranged and a filter chamber in which a filter is arranged and having one end portion and the other end portion in an axial direction closed; an igniter assembled to the one end portion of the housing, for burning the gas generating agent; and a sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) accommodating the gas generating agent in a hermetically sealed state, the housing having in a portion defining the filter chamber, a gas discharge opening for discharging a gas to outside, and the filter having a hollow portion extending along the axial direction of the housing and reaching an axial end surface located on a side of the combustion chamber, a partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) axially dividing a space in the housing so as to form the combustion chamber at a position on a side of the one end portion of the housing and to form the filter chamber at a position on a side of the other end portion of the housing; characterized by the partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) being made of a member composed of a material higher in mechanical strength than the sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) such that at least a part of a portion opposed to the hollow portion of the filter bursts with increase in pressure in the combustion chamber as a result of burning of the gas generating agent to provide a communication hole which allows communication between the combustion chamber and the filter chamber the sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) being made of a member composed of a material lower in mechanical strength than the partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) such that at least a part of a portion opposed to the hollow portion of the filter bursts or melts with increase in pressure or temperature of the combustion chamber as a result of burning of the gas generating agent, the partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) being arranged outside the sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) so as to abut on the axial end surface of the filter located on the side of the combustion chamber, and the sealed container being arranged such that an axial end portion located on the side of the filter chamber abuts on the partition member. an elongated cylindrical housing containing a combustion chamber in which a gas generating agent is arranged and a filter chamber in which a filter is arranged and having one end portion and the other end portion in an axial direction closed; an igniter assembled to the one end portion of the housing, for burning the gas generating agent; and a sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) accommodating the gas generating agent in a hermetically sealed state, the housing having in a portion defining the filter chamber, a gas discharge opening for discharging a gas to outside, and the filter having a hollow portion extending along the axial direction of the housing and reaching an axial end surface located on a side of the combustion chamber, a partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) axially dividing a space in the housing so as to form the combustion chamber at a position on a side of the one end portion of the housing and to form the filter chamber at a position on a side of the other end portion of the housing; characterized by the partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) being made of a member composed of a material higher in mechanical strength than the sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) such that at least a part of a portion opposed to the hollow portion of the filter bursts with increase in pressure in the combustion chamber as a result of burning of the gas generating agent to provide a communication hole which allows communication between the combustion chamber and the filter chamber the sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) being made of a member composed of a material lower in mechanical strength than the partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) such that at least a part of a portion opposed to the hollow portion of the filter bursts or melts with increase in pressure or temperature of the combustion chamber as a result of burning of the gas generating agent, the partition member (70A, 70A1, 70A2, 70A3, 70B, 70C, 70D) being arranged outside the sealed container (50A, 50A1, 50A2, 50B, 50C, 50C1, 50D) so as to abut on the axial end surface of the filter located on the side of the combustion chamber, and the sealed container being arranged such that an axial end portion located on the side of the filter chamber abuts on the partition member.