An air conditioning system for a vehicle is provided with: an air conditioning device having a main air blower, a main duct, and a heat exchange section, the air conditioning device converting air, which is sucked into the main duct by the main air blower, into air conditioning air by the heat exchange section and blowing the air conditioning air into the vehicle interior; a suction opening disposed in the vicinity of an occupant's seat; and a sub-duct having one end connected to the suction opening and sucking air from the suction opening. The air conditioning device sucks the air, which is sucked into the sub-duct, into the main duct and blows the air again into the vehicle interior. In the air conditioning system, the air conditioning air blown into the vehicle interior by the air conditioning device is sucked from the suction opening disposed in the vicinity of the occupant's seat. This causes the air conditioning air to be collected and at the same time the air conditioning air flowing rearward beyond the suction opening to be reduced, and as a result, comfortable zone air conditioning can be performed. In a zone air conditioning mode, air conditioning air having a desired temperature is generated by the heat exchange section. This means that the installation of a heat exchange section exclusive for the zone air conditioning is not essential, and as a result, the system can be simplified and the cost can be reduced.