Abstract: A gas-liquid separating apparatus for separating gas and liquid of a gas-liquid mixture includes a drum, and a separator disposed in the drum. The gas-liquid enters the separator into a cylinder of the separator in a tangential direction, and thus flows along the inner wall surface of the cylinder so that centrifugal separation of the gas and liquid is effected. The gas is discharged into a gas-phase section of the drum. At least part of the primary isolated liquid is decelerated by a perforated plate of the separator from which the liquid flows into a liquid-phase section of the drum. Because the primary isolated liquid flowing into the liquid-phase section of the drum has a slow outflow velocity, it tends to flow upwardly in the vicinity of the cylinder due to the buoyancy of gas still entrained in the liquid. Accordingly, the gravitational separation of the entrained gas and liquid is facilitated.