A vehicle air conditioning system performing individual air conditioning in four zones for left and right spaces of front and rear seats includes a front seat heating, ventilation, and air conditioner (HVAC) separately supplying air having passed through left and right flow paths of a front seat flow path into the left and right spaces of the front seat to perform two-zone individual air conditioning for the front seat. A flow guide is provided in an upstream side space of an evaporator in an internal space of the air conditioning casing of the front seat HVAC to divide the upstream side space of the evaporator to have a left flow path and a right flow path. The flow guide and a side portion of the air conditioning casing opposite to the flow guide have a curved stepped portion in cross-section.