An ejector refrigeration cycle includes a bypass passage that guides a refrigerant on an outlet side of an evaporator drawn from a refrigerant suction port of an ejector to a suction port side of a compressor while bypassing a diffuser passage of the ejector. A differential pressure regulating valve is disposed as a bypass flow-rate adjustment device that adjusts a bypass flow rate of the refrigerant circulating though the bypass passage. An enlarged portion for gradually enlarging the passage area is formed at a most downstream part of the refrigerant flow in the bypass passage. During a low-load operation, the differential pressure regulating valve increases the bypass flow rate, thereby allowing the refrigerant to flow into the evaporator connected to the upstream side of a refrigerant suction port using the suction effect of the compressor.