A refrigeration cycle device is provided with: a refrigeration cycle formed by sequentially connecting by means of piping a first compressor (1), a heat dissipater, an expander (8) for expanding a refrigerant which has passed through the heat dissipater and recovering power from the refrigerant, and an evaporator; bypass piping (24) having one end connected to the discharge piping of the expander and the other end connected to the suction piping of the first compressor; a pressure sensor (85) and a temperature sensor (91) for respectively detecting the suction pressure and the suction temperature of the expander (8) as the physical quantities of the refrigerant sucked by the expander (8); a bypass valve (10) provided to the bypass piping (24) and regulating the flow rate of the refrigerant; and a control device (103) for controlling the extent of opening of the bypass valve (10). The control device (103) determines the appropriate discharge pressure of the expander (8) on the basis of the suction pressure and the suction temperature of the expander and opens the bypass valve (10) when the pressure at which the expander (8) discharges the refrigerant is higher than the determined appropriate discharge pressure.