The air conditioner of the present invention includes: a plurality of indoor units which is respectively provided with an indoor heat exchanger; a plurality of outdoor units which is respectively provided with a water-refrigerant heat exchanger for carrying out heat exchange between refrigerant and heat source water, connected to the plurality of indoor units via refrigerant paths, and respectively mounted with outdoor unit PCBs; a heat source water path which is connected to the water-refrigerant heat exchangers; a pump which is mounted on the heat source water path; a variable flow rate valve which is mounted on the heat source water path and has an adjustable degree of opening; a central controller which controls the plurality of outdoor units; and a variable flow rate valve control board which controls the opening degree of the variable flow rate valve so as to control the flow rate of the heat source water. The variable flow rate valve control board is connected to the outdoor unit PCBs via first communication lines and to the central controller via second communication lines, which are different from the first ones in the communication mode, and converts communication protocols between the central controller and the outdoor unit PCBs such that the central controller may control the both of the outdoor units and the variable flow rate valve via the variable flow rate valve control board and the structure may be simplified over the case in which additional gateways are provided between the central controller and the outdoor units.