A refrigeration cycle apparatus, comprising: a main compressor compressing a refrigerant; a radiator radiating heat of the refrigerant compressed by the main compressor; an expander reducing a pressure of the refrigerant that has passed through the radiator; an evaporator evaporating the refrigerant that has been depressurized by the expander; a sub-compressor having a discharge side connected to a midway position of a compression process of the main compressor, the sub-compressor using power, which is generated in the expander when reducing the pressure of the refrigerant, to compress a portion of the refrigerant passing through the evaporator to an intermediate pressure; characterized by an intermediate-pressure bypass connecting a refrigerant outflow side of the sub-compressor and a refrigerant inflow side of the main compressor to each other; an intermediate-pressure bypass valve being provided in the intermediate-pressure bypass, the intermediate-pressure bypass valve controlling a flow rate of the refrigerant flowing through the intermediate-pressure bypass; a pre-expansion valve being provided between a refrigerant outflow side of the radiator and a refrigerant inflow side of the expander, the pre-expansion valve reducing the pressure of the refrigerant flowing into the expander; and a controller controlling an operation of the intermediate-pressure bypass valve and an operation of the pre-expansion valve, wherein the controller 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. a main compressor compressing a refrigerant; a radiator radiating heat of the refrigerant compressed by the main compressor; an expander reducing a pressure of the refrigerant that has passed through the radiator; an evaporator evaporating the refrigerant that has been depressurized by the expander; a sub-compressor having a discharge side connected to a midway position of a compression process of the main compressor, the sub-compressor using power, which is generated in the expander when reducing the pressure of the refrigerant, to compress a portion of the refrigerant passing through the evaporator to an intermediate pressure; characterized by an intermediate-pressure bypass connecting a refrigerant outflow side of the sub-compressor and a refrigerant inflow side of the main compressor to each other; an intermediate-pressure bypass valve being provided in the intermediate-pressure bypass, the intermediate-pressure bypass valve controlling a flow rate of the refrigerant flowing through the intermediate-pressure bypass; a pre-expansion valve being provided between a refrigerant outflow side of the radiator and a refrigerant inflow side of the expander, the pre-expansion valve reducing the pressure of the refrigerant flowing into the expander; and a controller controlling an operation of the intermediate-pressure bypass valve and an operation of the pre-expansion valve, wherein the controller 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.