A refrigeration cycle apparatus comprising: a low temperature-side refrigerant circuit including a low temperature-side compressor which compresses a low temperature-side refrigerant, a cascade heat exchanger which functions as a radiator of the low temperature-side refrigerant, low temperature-side expanding means, and a low temperature-side heat exchanger which functions as an evaporator of the low temperature-side refrigerant; a high temperature-side refrigerant circuit including a high temperature-side compressor which compresses a high temperature-side refrigerant, a high temperature-side heat exchanger which functions as a radiator of the high temperature-side refrigerant, high temperature-side expanding means, and the cascade heat exchanger which functions as an evaporator of the high temperature-side refrigerant by radiation of the low temperature-side refrigerant; a first temperature sensor which detects a temperature of the high temperature-side compressor or a temperature of a high pressure-side refrigerant pipe extending to the high temperature-side heat exchanger; a second temperature sensor which detects a temperature of a heating medium which exchanges heat with the high temperature-side refrigerant in the high temperature-side heat exchanger; and a control apparatus, characterized in that when a temperature detected by the second temperature sensor is higher than a temperature detected by the first temperature sensor by a predetermined temperature difference or more, the control apparatus is configured to start the high temperature-side compressor and then, to start the low temperature-side compressor, wherein the refrigeration cycle apparatus further comprises a first superheat degree detecting means which detects a superheat degree of a refrigerant discharged from the high temperature-side compressor in the high temperature-side refrigerant circuit, and wherein the control apparatus is configured to reduce a circulation amount of the high temperature-side refrigerant to a value equal to or lower than a predetermined value and to operate the refrigeration cycle apparatus until the superheat degree detected by the first superheat degree detecting means exceeds a predetermined first superheat degree. a low temperature-side refrigerant circuit including a low temperature-side compressor which compresses a low temperature-side refrigerant, a cascade heat exchanger which functions as a radiator of the low temperature-side refrigerant, low temperature-side expanding means, and a low temperature-side heat exchanger which functions as an evaporator of the low temperature-side refrigerant; a high temperature-side refrigerant circuit including a high temperature-side compressor which compresses a high temperature-side refrigerant, a high temperature-side heat exchanger which functions as a radiator of the high temperature-side refrigerant, high temperature-side expanding means, and the cascade heat exchanger which functions as an evaporator of the high temperature-side refrigerant by radiation of the low temperature-side refrigerant; a first temperature sensor which detects a temperature of the high temperature-side compressor or a temperature of a high pressure-side refrigerant pipe extending to the high temperature-side heat exchanger; a second temperature sensor which detects a temperature of a heating medium which exchanges heat with the high temperature-side refrigerant in the high temperature-side heat exchanger; and a control apparatus, characterized in that when a temperature detected by the second temperature sensor is higher than a temperature detected by the first temperature sensor by a predetermined temperature difference or more, the control apparatus is configured to start the high temperature-side compressor and then, to start the low temperature-side compressor, wherein the refrigeration cycle apparatus further comprises a first superheat degree detecting means which detects a superheat degree of a refrigerant discharged from the high temperature-side compressor in the high temperature-side refrigerant circuit, and wherein the control apparatus is configured to reduce a circulation amount of the high temperature-side refrigerant to a value equal to or lower than a predetermined value and to operate the refrigeration cycle apparatus until the superheat degree detected by the first superheat degree detecting means exceeds a predetermined first superheat degree.