A vehicular air conditioner includes an air conditioning, a heater core, a heat pump cycle unit, a temperature detector, and a controller. The heat pump cycle unit includes a first inside heat exchanger disposed downstream of the heater core in a flow direction of a conditioning air, a second inside heat exchanger disposed upstream of the heater core in the flow direction of the conditioning air, and an outside heat exchanger. The temperature detector is configured to detect a passage air temperature, the passage air temperature being a temperature of the conditioning air that has passed through the heater core. The controller is configured to selectively switch a circuit layout of the heat pump cycle unit between a cooling circuit, a heating circuit, and a dehumidifying-heating circuit based on the passage air temperature.