A refrigeration cycle apparatus achieves efficient operation by constantly recovering power in a wide operating range. The refrigeration cycle apparatus regulates a pressure of a high pressure side by changing either one or both of an opening degree of the intermediate-pressure bypass valve and an opening degree of the pre-expansion valve on the basis of a density ratio that is obtained from an inflow refrigerant density of the expander and an inflow refrigerant density of the sub-compressor in an actual operating state and a design volume ratio that has been expected at the time of design and that is obtained from a stroke volume of the sub-compressor, a stroke volume of the expander, and a ratio of a flow rate of the refrigerant flowing to the sub-compressor.