A refrigeration cycle apparatus (100, 101) comprising: a refrigerant circuit including a compressor, a condenser (4, 6), an expansion device, and an evaporator (4, 6); an oil separator provided at a refrigerant discharge side of the compressor and configured to separate refrigerant and a refrigerating machine oil; a first oil return path (9, 11) comprising a first connection pipe and a second connection pipe, the first oil return path (9, 11) connecting the oil separator to a refrigerant suction side of the compressor; a flow control device provided on the first oil return path (9, 11) and configured to reduce pressure of the refrigerant and the refrigerating machine oil; an oil reservoir pipe provided so as to branch from the first oil return path (9, 11) between the flow control device and the refrigerant suction side of the compressor and configured to store the refrigerating machine oil; a second oil return path (13, 15) on which the oil reservoir is provided, the second oil return path (13, 15) connecting the first connection pipe between the oil separator and the flow control device to the second connection pipe between the flow control device and the refrigerant suction side of the compressor, or connecting a pipe between the oil separator and the refrigerant discharge side of the compressor to the second connection pipe between the flow control device and the refrigerant suction side of the compressor; a first opening and closing device provided on the second oil return path (13, 15) and configured to control flow of the refrigerant and the refrigerating machine oil; and a controller configured to control the first opening and closing device to return the refrigerating machine oil via the second oil return path (13, 15) to the refrigerant suction side of the compressor, and wherein the oil reservoir pipe is connected at an upper side so as to branch downward from the second connection pipe such that refrigerating machine oil flowing through the second connection pipe flows down due to gravity during continuous operation and is connected at a lower portion thereof to the second oil return path (13, 15); and wherein the inner diameter is set to be small such that the flow speed of the refrigerant gas increases as the refrigerating machine oil flows together with the refrigerant gas from the lower end toward the upper end of the oil reservoir pipe against gravity due to a pressure difference from a lower end to an upper end, and wherein the first opening and closing device is provided between the oil reservoir pipe and the oil separator, and wherein the controller is configured to switch the first opening and closing device to open, and to switch the first opening and closing device to close after the refrigerating machine oil stored in the oil reservoir pipe is returned to the compressor. a refrigerant circuit including a compressor, a condenser (4, 6), an expansion device, and an evaporator (4, 6); an oil separator provided at a refrigerant discharge side of the compressor and configured to separate refrigerant and a refrigerating machine oil; a first oil return path (9, 11) comprising a first connection pipe and a second connection pipe, the first oil return path (9, 11) connecting the oil separator to a refrigerant suction side of the compressor; a flow control device provided on the first oil return path (9, 11) and configured to reduce pressure of the refrigerant and the refrigerating machine oil; an oil reservoir pipe provided so as to branch from the first oil return path (9, 11) between the flow control device and the refrigerant suction side of the compressor and configured to store the refrigerating machine oil; a second oil return path (13, 15) on which the oil reservoir is provided, the second oil return path (13, 15) connecting the first connection pipe between the oil separator and the flow control device to the second connection pipe between the flow control device and the refrigerant suction side of the compressor, or connecting a pipe between the oil separator and the refrigerant discharge side of the compressor to the second connection pipe between the flow control device and the refrigerant suction side of the compressor; a first opening and closing device provided on the second oil return path (13, 15) and configured to control flow of the refrigerant and the refrigerating machine oil; and a controller configured to control the first opening and closing device to return the refrigerating machine oil via the second oil return path (13, 15) to the refrigerant suction side of the compressor, and wherein the oil reservoir pipe is connected at an upper side so as to branch downward from the second connection pipe such that refrigerating machine oil flowing through the second connection pipe flows down due to gravity during continuous operation and is connected at a lower portion thereof to the second oil return path (13, 15); and wherein the inner diameter is set to be small such that the flow speed of the refrigerant gas increases as the refrigerating machine oil flows together with the refrigerant gas from the lower end toward the upper end of the oil reservoir pipe against gravity due to a pressure difference from a lower end to an upper end, and wherein the first opening and closing device is provided between the oil reservoir pipe and the oil separator, and wherein the controller is configured to switch the first opening and closing device to open, and to switch the first opening and closing device to close after the refrigerating machine oil stored in the oil reservoir pipe is returned to the compressor.