Disclosed is an air conditioning system including a duct having an intake passage through which outdoor air is induced and a discharge passage through which indoor air is discharged, suction and discharging fans respectively installed in the intake and discharge passages, a dehumidifier having a desiccant wheel rotatably mounted on an opening of the partition, a regenerating heater for heating air induced into the dehumidifier, a regenerating heat exchanger provided on the intake and discharge passages in the vicinity of an indoor side with reference to the dehumidifier to heat-exchange air flowing along the intake passage with air flowing along the discharge passage, and a heat pump provided on the duct to heat-exchange outdoor air that has passed through the regenerating heat exchanger and discharging the heat-exchanged air to an indoor space.