To provide a gas-liquid separator capable of keeping high gas-liquid separating efficiency by efficiently separating the condensate flowing down along an inner peripheral wall face of a steam pipe conduit.

An inlet 1 and an outlet 2 are coaxially formed on separator casings 3, 13. A diameter-enlarged part 8 is formed on a central part of the separator casing 3 to incorporate a cylindrical liquid collecting member 4. A liquid passage 5 is formed between the liquid collecting member 4 and the separator casing 3. A liquid outlet 6 is formed on a lower end part of the liquid passage 5. The condensate flowing down along the inner peripheral wall face of the steam pipe conduit is allowed to flow into the inlet 1 of the separator casing 3, and passed through the liquid passage 5 from the liquid collecting member 4 to be discharged to the external from a valve 11, and further the condensate is captured in the separator casing 13 to be discharged to the external from a trap outlet 17, whereby the condensate and the steam are separated from each other.