An air conditioning system which includes a plurality of outdoor units (2a, 2b) and a plurality of indoor units (3a, 3b) connected in parallel and undergoes autonomous decentralized control in a normal period such that a predetermined state quantity in each of the indoor units (3a, 3b) and each of the outdoor units (2a, 2b) is in a predetermined allowable range set in advance, the system comprising: a plurality of indoor unit control parts (50a, 50b) provided to respectively correspond to the indoor units (3a, 3b); and a plurality of outdoor unit control parts (40a, 40b) provided to respectively correspond to the outdoor units (2a, 2b), wherein the indoor unit control parts (50a, 50b) and the outdoor unit control parts (40a, 40b) enable intercommunication, in a transition period where a target value in any of the indoor units (3a, 3b) is changed, the indoor unit control part (50a, 50b) corresponding to the indoor unit (3a, 3b) in which the target value is changed is configured to transmit information regarding a change of the target value to the outdoor unit control parts (40a, 40b), the outdoor unit control parts (40a, 40b) are configured to perform intercommunication, and to determine, among the plurality of the outdoor units (2a, 2b), the outdoor unit which operates to correspond to the indoor unit (3a, 3b) in which the target value is changed, according to an algorithm stored in advance, a subdomain is formed between the outdoor unit control part (40a, 40b) corresponding to the determined outdoor unit and the indoor unit control part (50a, 50b) corresponding to the indoor unit in which the target value is changed, and the outdoor unit control part and the indoor unit control part are virtually grouped together, and the indoor unit control part (50a, 50b) and the outdoor unit control part (40a, 40b) which are virtually grouped together respectively generate control commands for tracking the changed target value and enabling an amount of variation in the state quantity, in the indoor unit (3a, 3b) and the outdoor unit (2a, 2b) respectively corresponding to the indoor unit control part and the outdoor unit control part which are virtually grouped together, to be in a predetermined range through communication therebetween, and transmit the generated control commands to the corresponding indoor unit and outdoor unit. a plurality of indoor unit control parts (50a, 50b) provided to respectively correspond to the indoor units (3a, 3b); and a plurality of outdoor unit control parts (40a, 40b) provided to respectively correspond to the outdoor units (2a, 2b), wherein the indoor unit control parts (50a, 50b) and the outdoor unit control parts (40a, 40b) enable intercommunication, in a transition period where a target value in any of the indoor units (3a, 3b) is changed, the indoor unit control part (50a, 50b) corresponding to the indoor unit (3a, 3b) in which the target value is changed is configured to transmit information regarding a change of the target value to the outdoor unit control parts (40a, 40b), the outdoor unit control parts (40a, 40b) are configured to perform intercommunication, and to determine, among the plurality of the outdoor units (2a, 2b), the outdoor unit which operates to correspond to the indoor unit (3a, 3b) in which the target value is changed, according to an algorithm stored in advance, a subdomain is formed between the outdoor unit control part (40a, 40b) corresponding to the determined outdoor unit and the indoor unit control part (50a, 50b) corresponding to the indoor unit in which the target value is changed, and the outdoor unit control part and the indoor unit control part are virtually grouped together, and the indoor unit control part (50a, 50b) and the outdoor unit control part (40a, 40b) which are virtually grouped together respectively generate control commands for tracking the changed target value and enabling an amount of variation in the state quantity, in the indoor unit (3a, 3b) and the outdoor unit (2a, 2b) respectively corresponding to the indoor unit control part and the outdoor unit control part which are virtually grouped together, to be in a predetermined range through communication therebetween, and transmit the generated control commands to the corresponding indoor unit and outdoor unit.