A gas-liquid separator that separates gas and liquid from a gas-liquid mixture, the gas-liquid separator comprising: a body portion having a cylindrical shape; an introduction passage provided in a state of communicating with the body portion , the gas-liquid mixture being introduced through the introduction passage ; a rectifying plate (50; 150) to rectify the gas-liquid mixture, wherein the rectifying plate (50; 150) is attached to the body portion to extend in a chord length direction of a circular arc formed by a barrel of the body portion; and an exhaust flow passage provided for gas from which liquid is separated, wherein the rectifying plate (50; 150) has a narrow width portion configured such that a distance between the rectifying plate and an inner wall of the body portion gradually decreases toward an end portion from which the gas-liquid mixture flows out, and a swirl portion in the body portion is formed by the body portion extending in an up-and-down direction and a partition plate (60; 160; 260) provided at a position lower than the introduction passage, characterized in that an insertion portion of the exhaust flow passage is inserted into the body portion , and the insertion portion extends by an extension length that allows the insertion portion to extend downward from an upper end portion of the body portion towards a position of a height of an upper end of an extending portion (51; 151) of the rectifying plate, the extending portion extending in a horizontal direction, wherein either the insertion portion extends downward to stop at the position of the height of the extending portion of the rectifying plate (50; 150), or the insertion portion extends downward to stop before the insertion portion reaches the position of the height of the extending portion of the rectifying plate (50; 150). a body portion having a cylindrical shape; an introduction passage provided in a state of communicating with the body portion , the gas-liquid mixture being introduced through the introduction passage ; a rectifying plate (50; 150) to rectify the gas-liquid mixture, wherein the rectifying plate (50; 150) is attached to the body portion to extend in a chord length direction of a circular arc formed by a barrel of the body portion; and an exhaust flow passage provided for gas from which liquid is separated, wherein the rectifying plate (50; 150) has a narrow width portion configured such that a distance between the rectifying plate and an inner wall of the body portion gradually decreases toward an end portion from which the gas-liquid mixture flows out, and a swirl portion in the body portion is formed by the body portion extending in an up-and-down direction and a partition plate (60; 160; 260) provided at a position lower than the introduction passage, characterized in that an insertion portion of the exhaust flow passage is inserted into the body portion , and the insertion portion extends by an extension length that allows the insertion portion to extend downward from an upper end portion of the body portion towards a position of a height of an upper end of an extending portion (51; 151) of the rectifying plate, the extending portion extending in a horizontal direction, wherein either the insertion portion extends downward to stop at the position of the height of the extending portion of the rectifying plate (50; 150), or the insertion portion extends downward to stop before the insertion portion reaches the position of the height of the extending portion of the rectifying plate (50; 150). <EOS>