In a hybrid vehicle air conditioning system in which coolant is supplied to a heater core from a vehicle running engine, for heating, a demand of the operation of the vehicle running engine is controlled to obtain respective set coolant temperatures TWS2 for target air-outlet temperature TAO of air sent out into a passenger compartment during a bilevel mode operation and TWS1 for the target air-outlet temperature TAO during a foot mode operation by setting the set coolant temperature TWS2 higher than the set coolant temperature TWS1.