Abstract: In an ejector cycle system, a variable throttle is disposed at an upstream side of an ejector. When high-pressure side refrigerant pressure in the ejector cycle system is approximately equal to or higher than critical pressure of the refrigerant, the variable throttle is fully opened. When the high-pressure side refrigerant pressure is approximately lower than the critical pressure of the refrigerant, a throttle open degree of the variable throttle is reduced from the fully open degree so that high-pressure side refrigerant is decompressed in two steps of the variable throttle and the ejector. Accordingly, in both cases of a high heat load and a low heat load of the ejector cycle system, COP of the ejector cycle system can be improved.