An ejector cycle system comprising: a compressor for sucking and compressing refrigerant; an exterior heat exchanger for performing heat-exchange between the refrigerant and air outside a compartment; an interior heat exchanger for performing heat-exchange between the refrigerant and air inside the compartment; an ejector including a nozzle for converting a pressure energy of high-pressure side refrigerant to a speed energy so that the high-pressure side refrigerant is decompressed and expanded, and a pressure-increasing portion in which the speed energy is converted to the pressure energy so that the pressure of refrigerant is increased while refrigerant discharged from the nozzle and gas refrigerant sucked from a low-pressure side are mixed; a gas-liquid separator for separating refrigerant into gas refrigerant and liquid refrigerant, and for storing refrigerant therein; a decompression unit for decompressing refrigerant flowing from the interior heat exchanger; and switching means (610, 620, 630, 631) for switching between a cooling operation in which heat is radiated from the compartment to an outside, and a heating operation where heat is radiated from the outside to the compartment, wherein the arrangement is such that the refrigerant-flowing direction in the cooling operation is identical to that in the heating operation in the interior heat exchanger in the cooling operation, the nozzle of the ejector decompresses the high-pressure side refrigerant, characterized in that in the heating operation, the decompression unit decompresses the high-pressure side refrigerant having passed through the interior heat exchanger. a compressor for sucking and compressing refrigerant; an exterior heat exchanger for performing heat-exchange between the refrigerant and air outside a compartment; an interior heat exchanger for performing heat-exchange between the refrigerant and air inside the compartment; an ejector including a nozzle for converting a pressure energy of high-pressure side refrigerant to a speed energy so that the high-pressure side refrigerant is decompressed and expanded, and a pressure-increasing portion in which the speed energy is converted to the pressure energy so that the pressure of refrigerant is increased while refrigerant discharged from the nozzle and gas refrigerant sucked from a low-pressure side are mixed; a gas-liquid separator for separating refrigerant into gas refrigerant and liquid refrigerant, and for storing refrigerant therein; a decompression unit for decompressing refrigerant flowing from the interior heat exchanger; and switching means (610, 620, 630, 631) for switching between a cooling operation in which heat is radiated from the compartment to an outside, and a heating operation where heat is radiated from the outside to the compartment, wherein the arrangement is such that the refrigerant-flowing direction in the cooling operation is identical to that in the heating operation in the interior heat exchanger in the cooling operation, the nozzle of the ejector decompresses the high-pressure side refrigerant, characterized in that in the heating operation, the decompression unit decompresses the high-pressure side refrigerant having passed through the interior heat exchanger.