A refrigeration cycle apparatus including a refrigerant circuit sequentially connecting, with pipes, a compressor, a refrigerant-flow switching device, an air-side heat exchanger, a main expansion valve, and a water-side heat exchanger, and configured to allow refrigerant to circulate in the refrigerant circuit, the refrigeration cycle apparatus comprising: a refrigerant amount adjustment tank arranged in parallel with the main expansion valve, and configured to store the refrigerant; an outside-air temperature sensor configured to measure an ambient temperature of the refrigerant amount adjustment tank; a low-pressure pressure sensor configured to measure a pressure of the refrigerant flowing into the compressor; a first refrigerant flow control valve provided to a pipe connected to one end of the refrigerant amount adjustment tank, the pipe being branched from a pipe connecting the air-side heat exchanger and the main expansion valve, the first refrigerant flow control valve being configured to adjust a flow rate of the refrigerant flowing into and out of the refrigerant amount adjustment tank on a basis of an opening degree of the first refrigerant flow control valve; a second refrigerant flow control valve provided to a pipe connected to an other end of the refrigerant amount adjustment tank, the pipe being branched from a pipe connecting the main expansion valve and the water-side heat exchanger, the second refrigerant flow control valve being configured to adjust a flow rate of the refrigerant flowing into and out of the refrigerant amount adjustment tank on a basis of an opening degree of the second refrigerant flow control valve; and a controller configured to control the compressor, the main expansion valve, the first refrigerant flow control valve, and the second refrigerant flow control valve, in cooling operation, the controller being configured to control the opening degree of the first refrigerant flow control valve on a basis of an outside-air temperature that is the ambient temperature of the refrigerant amount adjustment tank and an evaporating temperature of the refrigerant which is a saturation temperature of the refrigerant converted from the pressure measured by the low-pressure sensor. a refrigerant amount adjustment tank arranged in parallel with the main expansion valve, and configured to store the refrigerant; an outside-air temperature sensor configured to measure an ambient temperature of the refrigerant amount adjustment tank; a low-pressure pressure sensor configured to measure a pressure of the refrigerant flowing into the compressor; a first refrigerant flow control valve provided to a pipe connected to one end of the refrigerant amount adjustment tank, the pipe being branched from a pipe connecting the air-side heat exchanger and the main expansion valve, the first refrigerant flow control valve being configured to adjust a flow rate of the refrigerant flowing into and out of the refrigerant amount adjustment tank on a basis of an opening degree of the first refrigerant flow control valve; a second refrigerant flow control valve provided to a pipe connected to an other end of the refrigerant amount adjustment tank, the pipe being branched from a pipe connecting the main expansion valve and the water-side heat exchanger, the second refrigerant flow control valve being configured to adjust a flow rate of the refrigerant flowing into and out of the refrigerant amount adjustment tank on a basis of an opening degree of the second refrigerant flow control valve; and a controller configured to control the compressor, the main expansion valve, the first refrigerant flow control valve, and the second refrigerant flow control valve, in cooling operation, the controller being configured to control the opening degree of the first refrigerant flow control valve on a basis of an outside-air temperature that is the ambient temperature of the refrigerant amount adjustment tank and an evaporating temperature of the refrigerant which is a saturation temperature of the refrigerant converted from the pressure measured by the low-pressure sensor.