To provide a gas refrigerant separator capable of relaxing restriction on an attachment direction when incorporated in a refrigeration device, a gas refrigerant separator-cum-refrigerant flow divider to which a gas refrigerant separating mechanism in the gas refrigerant separator is applied, and an expansion valve and the refrigeration device.

The gas refrigerant separator-cum-refrigerant flow divider DR includes an introduction chamber 10 having a circular cross section, a speed increase chamber 20 having a circular cross section, and a delivery chamber 30 having a circular cross section, and the chambers are disposed serially and coaxially. The delivery chamber 30 introduces therein a refrigerant from a refrigerant introduction opening 14 along the inner wall surface of the chamber and swirls the refrigerant. The speed increase chamber 20 increases the speed of the swirl flow of the refrigerant flowing from the introduction chamber 10, and discharges the refrigerant from a communication opening 21 which is located at the front end to the delivery chamber 30. The delivery chamber 30 has a diameter larger than the diameter of the communication opening 21 at the tip of the speed increase chamber 20. Also, the gas refrigerant separator-cum-refrigerant flow divider DR includes a gas refrigerant extraction pipe Pg for extracting a gas refrigerant from the center of the swirling refrigerant flow, and a refrigerant delivery pipe Pd for delivering the refrigerant from which the gas refrigerant has been extracted.