A refrigeration cycle apparatus (300, 301, 302, 302A) comprising: a refrigerant circuit in which refrigerant circulates in the order of a compressor, an oil separator, a first heat exchanger, a decompressing apparatus, and a second heat exchanger and returns to the compressor; an oil reservoir configured to store refrigeration oil; a first pipe that connects the oil separator and the oil reservoir, the first pipe being configured to send the refrigeration oil separated by the oil separator to the oil reservoir; a first valve provided at the first pipe; a second pipe that connects the oil reservoir and a suction side of the compressor; a second valve provided at the second pipe; a third pipe that connects the oil reservoir and the suction side of the compressor at a position lower than a position at which the second pipe is connected to the oil reservoir; and a third valve provided at the third pipe, wherein the first to third valves (11, 12, 13) are closed in a non-operational period of the compressor; characterized in that the refrigeration cycle apparatus (300, 301, 302, 302A) further comprises: an oil concentration sensor configured to detect an oil concentration of liquid stored in the oil reservoir; and a controller (100, 101, 102) configured to control respective degrees of opening of the first to third valves (11, 12, 13) to allow the oil concentration detected by the oil concentration sensor to coincide with a defined concentration, wherein, when the oil concentration detected by the oil concentration sensor is lower than the defined concentration, the controller (100, 101, 102) is configured to decrease the degree of opening of the first valve to be less than the degree of opening of the first valve when the oil concentration is higher than the defined concentration. a refrigerant circuit in which refrigerant circulates in the order of a compressor, an oil separator, a first heat exchanger, a decompressing apparatus, and a second heat exchanger and returns to the compressor; an oil reservoir configured to store refrigeration oil; a first pipe that connects the oil separator and the oil reservoir, the first pipe being configured to send the refrigeration oil separated by the oil separator to the oil reservoir; a first valve provided at the first pipe; a second pipe that connects the oil reservoir and a suction side of the compressor; a second valve provided at the second pipe; a third pipe that connects the oil reservoir and the suction side of the compressor at a position lower than a position at which the second pipe is connected to the oil reservoir; and a third valve provided at the third pipe, wherein the first to third valves (11, 12, 13) are closed in a non-operational period of the compressor; characterized in that the refrigeration cycle apparatus (300, 301, 302, 302A) further comprises: an oil concentration sensor configured to detect an oil concentration of liquid stored in the oil reservoir; and a controller (100, 101, 102) configured to control respective degrees of opening of the first to third valves (11, 12, 13) to allow the oil concentration detected by the oil concentration sensor to coincide with a defined concentration, wherein, when the oil concentration detected by the oil concentration sensor is lower than the defined concentration, the controller (100, 101, 102) is configured to decrease the degree of opening of the first valve to be less than the degree of opening of the first valve when the oil concentration is higher than the defined concentration. an oil concentration sensor configured to detect an oil concentration of liquid stored in the oil reservoir; and a controller (100, 101, 102) configured to control respective degrees of opening of the first to third valves (11, 12, 13) to allow the oil concentration detected by the oil concentration sensor to coincide with a defined concentration, wherein, when the oil concentration detected by the oil concentration sensor is lower than the defined concentration, the controller (100, 101, 102) is configured to decrease the degree of opening of the first valve to be less than the degree of opening of the first valve when the oil concentration is higher than the defined concentration.