An air-conditioning apparatus comprising: a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, an expansion unit and a use-side heat exchanger are connected by a refrigerant pipe, the refrigerant circuit being configured to cause refrigerant to circulate therein; an indoor unit installed in an air-conditioning target space, and including the use-side heat exchanger; an indoor air-sending device configured to send air to the use-side heat exchanger; a refrigerant leakage detection device provided in the indoor unit, and configured to detect leakage of refrigerant in the air-conditioning target space; and a controller (14, 24) including a leakage determination unit configured to determine, based on a result of detection by the refrigerant detection device, whether leakage of refrigerant occurs or not, and an operation control unit configured to control the indoor air-sending device in accordance with the control mode determined by the control mode determining unit, characterized in that the controller (14, 24) is configured to execute entry of each of a normal control mode and a rarefying control mode, the normal control mode being a control mode in which the refrigerant circuit and the indoor air-sending device are controlled in accordance with an air-conditioning load, the rarefying control mode being a control mode in which the indoor air-sending device is operated at a rarefying rotation speed which is a higher rotation speed than that in the normal control mode, wherein the controller (14, 24) includes a control mode determining unit configured to determine, in a case where the leakage determination unit determines that leakage of refrigerant occurs, the rarefying control mode as a control mode to be set, a rarefying instruction transmission unit configured to transmit to an other air-conditioning apparatus a rarefying operation instruction for causing the other air-conditioning apparatus to operate in the rarefying control mode, the other air-conditioning apparatus being installed in the air-conditioning target space, and wherein in a case where it is determined that a rotation speed of the indoor air-sending device in the rarefying control mode is lower than a set rotation speed, the operation control unit causes the rarefying instruction transmission unit to transmit the rarefying operation instruction to the other air-conditioning apparatus. a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, an expansion unit and a use-side heat exchanger are connected by a refrigerant pipe, the refrigerant circuit being configured to cause refrigerant to circulate therein; an indoor unit installed in an air-conditioning target space, and including the use-side heat exchanger; an indoor air-sending device configured to send air to the use-side heat exchanger; a refrigerant leakage detection device provided in the indoor unit, and configured to detect leakage of refrigerant in the air-conditioning target space; and a controller (14, 24) including a leakage determination unit configured to determine, based on a result of detection by the refrigerant detection device, whether leakage of refrigerant occurs or not, and an operation control unit configured to control the indoor air-sending device in accordance with the control mode determined by the control mode determining unit, characterized in that the controller (14, 24) is configured to execute entry of each of a normal control mode and a rarefying control mode, the normal control mode being a control mode in which the refrigerant circuit and the indoor air-sending device are controlled in accordance with an air-conditioning load, the rarefying control mode being a control mode in which the indoor air-sending device is operated at a rarefying rotation speed which is a higher rotation speed than that in the normal control mode, wherein the controller (14, 24) includes a control mode determining unit configured to determine, in a case where the leakage determination unit determines that leakage of refrigerant occurs, the rarefying control mode as a control mode to be set, a rarefying instruction transmission unit configured to transmit to an other air-conditioning apparatus a rarefying operation instruction for causing the other air-conditioning apparatus to operate in the rarefying control mode, the other air-conditioning apparatus being installed in the air-conditioning target space, and wherein in a case where it is determined that a rotation speed of the indoor air-sending device in the rarefying control mode is lower than a set rotation speed, the operation control unit causes the rarefying instruction transmission unit to transmit the rarefying operation instruction to the other air-conditioning apparatus.