A vehicular air conditioner includes a partitioning portion which separates an inside of an air-conditioning casing into an inside-air passage through which an inside air flows and an outside-air passage through which an outside air flows, a cooling heat exchanger extending across both the inside-air passage and the outside-air passage, a heating heat exchanger heating the inside air and the outside air on a downstream side of the cooling heat exchanger in an air flow, and a restriction portion provided downstream of the cooing heat exchanger in the air flow and limiting inflow of the inside air into the outside-air passage on the way to the heating heat exchanger. The restriction portion is located in the inside-air passage between the cooing heat exchanger and the heating heat exchanger, and includes a first temperature regulation door that regulates a temperature of air supplied to the vehicle compartment.