A vehicle air-conditioning system that independently controls left-right air flow distribution in correspondence with left and right heat loads during a maximum cooling mode. In the system, blowout air flow is increased when driver seat side and passenger seat side air-mixing film members are both positioned in a maximum cooling position, and the heat load has risen in only one of a driver seat side space and a passenger seat side space in a passenger compartment. Further, each respective film member is operated to fully open a cool air bypass passage on the side on which the heat load has risen and the respective film member corresponding to the side on which the heat load has not risen significantly is operated to reduce the open area of the cool air bypass passage. At the same time, fan speed is increased to increase the air blow amount.