A gas generator comprising: a housing having a cylindrical circumferential wall portion provided with a plurality of gas discharge openings and having one end portion and the other end portion in an axial direction of the circumferential wall portion closed; a gas generating agent arranged in an accommodation space located in the housing ; an igniter assembled to the housing , for burning the gas generating agent ; and a sealing tape which closes the plurality of gas discharge openings , each of the plurality of gas discharge openings being opened as a portion of the sealing tape which closes each of the plurality of gas discharge openings is cleaved with increase in pressure in the accommodation space as a result of burning of the gas generating agent , the plurality of gas discharge openings including gas discharge openings set to be different from one another in opening pressure expressed as F×t×C/S so as to be opened stepwise with increase in pressure in the accommodation space as a result of burning of the gas generating agent , where F represents shear strength of the sealing tape , t represents a thickness of the portion of the sealing tape which closes each of the plurality of gas discharge openings , C represents a circumferential length of each of the plurality of gas discharge openings , and S represents an opening area of each of the plurality of gas discharge openings , characterized in that a condition of T ≤ 1.8 [mm] and SA ≥ 60 [mm 2 ] being satisfied, where T represents a thickness of a portion of the housing which defines the accommodation space and SA represents a total opening area of the plurality of gas discharge openings , and at least one of the plurality of gas discharge openings being in a shape of an elongated hole different in opening width in directions orthogonal to each other. a housing having a cylindrical circumferential wall portion provided with a plurality of gas discharge openings and having one end portion and the other end portion in an axial direction of the circumferential wall portion closed; a gas generating agent arranged in an accommodation space located in the housing ; an igniter assembled to the housing , for burning the gas generating agent ; and a sealing tape which closes the plurality of gas discharge openings , each of the plurality of gas discharge openings being opened as a portion of the sealing tape which closes each of the plurality of gas discharge openings is cleaved with increase in pressure in the accommodation space as a result of burning of the gas generating agent , the plurality of gas discharge openings including gas discharge openings set to be different from one another in opening pressure expressed as F×t×C/S so as to be opened stepwise with increase in pressure in the accommodation space as a result of burning of the gas generating agent , where F represents shear strength of the sealing tape , t represents a thickness of the portion of the sealing tape which closes each of the plurality of gas discharge openings , C represents a circumferential length of each of the plurality of gas discharge openings , and S represents an opening area of each of the plurality of gas discharge openings , characterized in that a condition of T ≤ 1.8 [mm] and SA ≥ 60 [mm 2 ] being satisfied, where T represents a thickness of a portion of the housing which defines the accommodation space and SA represents a total opening area of the plurality of gas discharge openings , and at least one of the plurality of gas discharge openings being in a shape of an elongated hole different in opening width in directions orthogonal to each other. <EOS>