A refrigeration cycle apparatus, comprising: a refrigerant circuit connecting a compressor, a first heat exchanger, an expansion device, and a second heat exchanger by piping, the refrigerant circuit circulating a refrigerant that transmits in a supercritical state, wherein one of the first heat exchanger and the second heat exchanger is operated as a gas cooler by making the refrigerant in a supercritical state flow therethrough, the other one of the first heat exchanger and the second heat exchanger is operated as a evaporator by making the refrigerant in a low-pressure two-phase state flow therethrough, the refrigeration cycle apparatus includes a heat medium sending device that changes a flow rate of a heat medium exchanging heat with the refrigerant in the gas cooler, and an outlet temperature sensor that is provided in any position in the passage from an outlet side of the gas cooler to the expansion device, the outlet temperature sensor detecting a temperature of the refrigerant on the outlet side of the gas cooler, and characterized in that an opening degree of the expansion device is controlled on the basis of a temperature difference between a refrigerant temperature (Tcc) at a first representative point in which an enthalpy of the refrigerant becomes substantially the same as the enthalpy of a critical point under the refrigerant pressure in the gas cooler and a detection temperature (Tco) of the outlet temperature sensor, and a rotation speed of the compressor and/or a rotation speed of the heat medium sending device is/are controlled on the basis of a temperature (Tc) at a second representative point that is a temperature different from the first representative point under the refrigerant pressure in the gas cooler. a refrigerant circuit connecting a compressor, a first heat exchanger, an expansion device, and a second heat exchanger by piping, the refrigerant circuit circulating a refrigerant that transmits in a supercritical state, wherein one of the first heat exchanger and the second heat exchanger is operated as a gas cooler by making the refrigerant in a supercritical state flow therethrough, the other one of the first heat exchanger and the second heat exchanger is operated as a evaporator by making the refrigerant in a low-pressure two-phase state flow therethrough, the refrigeration cycle apparatus includes a heat medium sending device that changes a flow rate of a heat medium exchanging heat with the refrigerant in the gas cooler, and an outlet temperature sensor that is provided in any position in the passage from an outlet side of the gas cooler to the expansion device, the outlet temperature sensor detecting a temperature of the refrigerant on the outlet side of the gas cooler, and a heat medium sending device that changes a flow rate of a heat medium exchanging heat with the refrigerant in the gas cooler, and an outlet temperature sensor that is provided in any position in the passage from an outlet side of the gas cooler to the expansion device, the outlet temperature sensor detecting a temperature of the refrigerant on the outlet side of the gas cooler, and characterized in that an opening degree of the expansion device is controlled on the basis of a temperature difference between a refrigerant temperature (Tcc) at a first representative point in which an enthalpy of the refrigerant becomes substantially the same as the enthalpy of a critical point under the refrigerant pressure in the gas cooler and a detection temperature (Tco) of the outlet temperature sensor, and a rotation speed of the compressor and/or a rotation speed of the heat medium sending device is/are controlled on the basis of a temperature (Tc) at a second representative point that is a temperature different from the first representative point under the refrigerant pressure in the gas cooler.