The present invention provides a gas-liquid separator with enhanced performance and easy operation, enabling to perform gas-liquid separation such as advanced defoaming or degassing, and facilitating easy cleaning with CIP (Cleaning In Place) and COP (Cleaning Out Place) ability that meets sanitary specifications. This gas-liquid separator for gas-liquid separation performed by centrifugal force of an impeller mounted on a shaft which rotates in a casing comprises: a discharge impeller part providing discharge force to the passing fluid formed on an axial end of the impeller; a discharge outlet of the casing disposed in a position opposite the discharge impeller part; the other axial end of the impeller being formed to slide on the inner wall of the casing; an exhaust outlet of the casing disposed in a position opposite the sliding impeller part; vacuum means connected to the exhaust outlet; and a suction inlet of the casing disposed in a position between the discharge outlet and the exhaust outlet.