To stabilize the level of liquid-phase refrigerant accumulated in a gas/liquid separator and to prevent a lot of refrigerating machine oil from flowing into an evaporator.

A tank body 51 of the gas liquid separator 50 is formed into a conical flask shape gradually increasing a tank cross sectional area S as approaching to its lower side, so that the turning speed of the refrigerant adjacent to a liquid-phase refrigerant outlet 54 is reduced to stabilize the level of the liquid-phase refrigerant accumulated in the gas-liquid separator 50. The refrigerating machine oil flowing in the upper side of a refrigerant passage 61a is sucked by using a sucking pressure of a compressor 10 so as to be fed to the separated and selected compressor 10, while preventing a lot of refrigerating machine oil from flowing into the side of the evaporator 30.