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).