Disclosed is a rear air conditioner for a vehicle, which can improve the comfort of a rear seat in a vehicle by improving the temperature difference between a console vent and a B-pillar side while minimizing the increase in the temperature at the console vent side. The rear air conditioner for the vehicle is connected to a front air conditioner and supplies air conditioning airflow toward the rear seat of the vehicle, and comprises: a case of which one side is connected to the front air conditioner and the other side has a plurality of discharge ports for discharging the air into the interior of the vehicle; and an electric heater which is provided in the case and heats the air passing therethrough, wherein the electric heater is provided with a plurality of operating regions, of which at least one operates in linkage with an air conditioning mode.