The air conditioning system includes a plurality of partial networks (103), each of which has an indoor unit (102) of an air conditioning apparatus, and an outdoor unit (101) of the air conditioning apparatus connected therein, and the partial networks (103) are connected to each other via a connecting network (104). Each of gateway apparatuses (150) is connected to the indoor unit (102) and the outdoor unit (101) in a partial network to be managed, and to the connecting network (104). Via the connecting network (104) and other gateway apparatuses (150), each of the gateway apparatuses (150) relays communication between the indoor unit (102) and/or the outdoor unit (101) in the partial network to be managed, and the indoor unit (102) and/or the outdoor unit (101) in other partial networks.