To provide a gas-liquid separator in which gas-liquid separation of a fluid can be carried out without decentering the axis of a gas stream to be formed on the inside even when the fluid contains minute air bubbles and to provide a gas-liquid separating apparatus in which gas-liquid separation can be carried out efficiently while the internal pressure is adjusted by adjusting a flow rate control valve.

This gas-liquid separator is constituted of a flow rectifying part having such a shape that it converges almost from the center toward both ends, a gas collecting tool one end of which is communicated with one end of the flow rectifying part coaxially and which has a hollow part for collecting the gas, a liquid collecting tool one end of which is communicated with the other end of the flow rectifying part coaxially and which has a hollow part for collecting the liquid, a mixed fluid injecting hole opened on a flow rectifying tool in the tangential direction, a gas sending hole opened to the gas collecting tool on the axial line of the hollow part for collecting the gas and a liquid sending hole opened to the liquid collecting tool.