A controller to control an air conditioning apparatus, the air conditioning apparatus comprising: a compressor configured to compress a first heat medium; a first heat exchanger configured to exchange heat between the first heat medium and outdoor air; a second heat exchanger configured to exchange heat between the first heat medium and a second heat medium; a plurality of third heat exchangers (31, 41, 51) each configured to exchange heat between the second heat medium and indoor air; a plurality of flow rate control valves (33, 43, 53) each configured to control a flow rate of the second heat medium flowing through a corresponding one of the plurality of third heat exchangers (31, 41, 51); a pump configured to circulate the second heat medium between the plurality of third heat exchangers (31, 41, 51) and the second heat exchanger; and a first temperature sensor configured to detect a temperature of the second heat medium, characterized in that the controller is configured such that when the air conditioning apparatus is operating in a heating mode, and (i) when the temperature detected by the first temperature sensor is lower than a first determination value, the controller opens the flow rate control valve corresponding to a heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which a request for air conditioning has not been made, and closes the flow rate control valve corresponding to a heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has been made, and (ii) when the temperature detected by the first temperature sensor is higher than a second determination value higher than or equal to the first determination value, the controller opens the flow rate control valve corresponding to the heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has been made, and closes the flow rate control valve corresponding to the heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has not been made. a compressor configured to compress a first heat medium; a first heat exchanger configured to exchange heat between the first heat medium and outdoor air; a second heat exchanger configured to exchange heat between the first heat medium and a second heat medium; a plurality of third heat exchangers (31, 41, 51) each configured to exchange heat between the second heat medium and indoor air; a plurality of flow rate control valves (33, 43, 53) each configured to control a flow rate of the second heat medium flowing through a corresponding one of the plurality of third heat exchangers (31, 41, 51); a pump configured to circulate the second heat medium between the plurality of third heat exchangers (31, 41, 51) and the second heat exchanger; and a first temperature sensor configured to detect a temperature of the second heat medium, characterized in that the controller is configured such that when the air conditioning apparatus is operating in a heating mode, and (i) when the temperature detected by the first temperature sensor is lower than a first determination value, the controller opens the flow rate control valve corresponding to a heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which a request for air conditioning has not been made, and closes the flow rate control valve corresponding to a heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has been made, and (ii) when the temperature detected by the first temperature sensor is higher than a second determination value higher than or equal to the first determination value, the controller opens the flow rate control valve corresponding to the heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has been made, and closes the flow rate control valve corresponding to the heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has not been made. (i) when the temperature detected by the first temperature sensor is lower than a first determination value, the controller opens the flow rate control valve corresponding to a heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which a request for air conditioning has not been made, and closes the flow rate control valve corresponding to a heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has been made, and (ii) when the temperature detected by the first temperature sensor is higher than a second determination value higher than or equal to the first determination value, the controller opens the flow rate control valve corresponding to the heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has been made, and closes the flow rate control valve corresponding to the heat exchanger, of the plurality of third heat exchangers (31, 41, 51), to which the request for air conditioning has not been made.