An unified controller for controlling a plurality of air-conditioning systems which are capable of air-conditioning individual air-conditioning rooms of a building using different schemes. The unified controller is located under a Building Management System (BMS) controller which simultaneously manages a plurality of systems corresponding to arrangements of the building, and simultaneously controls a multiple air-conditioning system acting as one of the air-conditioning systems and a central air-conditioning system acting as the other one of the air-conditioning systems using a single control command. The unified controller performs error correction, addition of a new function, and update of pre-loaded functions upon receiving a request from the remote controller.