Disclosed herein is an air conditioning system. The conditioning system includes an air handling unit (AHU) configured to control outdoor air that is externally supplied, exhaust air that is outdoors discharged, and return air that is circulated indoors and supplied again, control the outdoor air or mixed air of the return air and the outdoor air at a set temperature, and supply cool/warm supply air indoors, at least one outdoor unit configured to supply a heat source for a heat exchange to the AHU, a controller configured to receive operating state data of the AHU and control an operation of the AHU through communication with the outdoor unit, and an interface unit connected to the controller and configured to output a control menu of the AHU, send data received through the control menu to the controller, and output a monitoring screen for the operating state of the AHU and the outdoor unit.