To improve separation efficiency of a gas-liquid separator for mainly separating droplet particles in a gas-liquid two-phase flow in a cold system of refrigerant circulation, a waste liquid distillation system, an exhaust gas treatment line and the like.

In the gas-liquid separator, an inflow pipe of the gas-liquid separator is spirally formed to generate a forced spiral flow when a gas-liquid two-phase flow passes through the spiral pipe, whereby droplet particles can be condensed on the peripheral wall surface of the spiral pipe by centrifugal force and a gas flow can be led to a gas-liquid separation tank body.