Controller of air conditioning apparatus, outdoor unit, relay unit, heat source unit, and air conditioning apparatus

An air conditioning apparatus includes: a second heat exchanger; a plurality of third heat exchangers; and a plurality of flow rate control valves. In a defrosting mode, when a heat exchanger that is not being requested to perform air conditioning includes a first device having a set temperature lower than or equal to a current room temperature and a second device which is set so as not to perform air conditioning, a controller is configured to control a first flow rate control valve corresponding to the first device and a second flow rate control valve corresponding to the second device such that a degree of opening of the first flow rate control valve is higher than or equal to a degree of opening of the second flow rate control valve.