A vehicular air conditioning system for saving energy includes: a first indoor cooling heat exchanger for suctioning in and cooling the air within or outside a vehicle; an indoor air conditioning heat exchanger installed on the downstream cooling heat exchanger for regulating the temperature of the applicable air, a refrigeration cycle connected to the applicable indoor air conditioning heat exchanger, a heating element mounted in the vehicle, and a circuit for the machine coolant circulating between the applicable heating element and the applicable first indoor cooling heat exchanger, and in which the air flow path for air flowing into the indoor air conditioning heat exchanger is structured by merging a flow path passing through the first indoor cooling heat exchanger to a flow path not passing through the first indoor cooling heat exchanger, and is also configured to allow switching to either of the two flow paths.