A vehicle air conditioner comprising: a heat pump device including a compressor that compresses a refrigerant, a first interior heat exchanger provided inside a vehicle cabin, a second interior heat exchanger provided inside the vehicle cabin and upstream of the first interior heat exchanger in an airflow direction, an exterior heat exchanger provided outside the vehicle cabin, and first and second pressure reducing valves, the heat pump device being formed by connecting together the compressor, the first and second interior heat exchangers, the pressure reducing valves (52, 53) and the exterior heat exchanger via refrigerant piping; an interior air-conditioning unit which houses the first and second interior heat exchangers and which includes a blower that blows air-conditioning air to the first and second interior heat exchangers, the interior air-conditioning unit being configured to produce conditioned air and supply the conditioned air into the vehicle cabin; and an air-conditioning controller configured to control the heat pump device and the interior air-conditioning unit, wherein the air-conditioning controller makes the heat pump device operate while making a switch between multiple operation modes including a second dehumidification and heating operation mode in which the refrigerant discharged from the compressor is circulated through the first interior heat exchanger, the second pressure reducing valve, the exterior heat exchanger, and the second interior heat exchanger in this order so that the first interior heat exchanger functions as a radiator and the second interior heat exchanger functions as a heat absorber. characterized in that it includes a first dehumidification and heating operation mode in which a refrigerant discharged from the compressor is circulated through the first interior heat exchanger; the first pressure reducing valve, the second interior heat exchanger, and the exterior heat exchanger in this order so that the first interior heat exchanger functions as a radiator and the second interior heat exchanger functions as heat absorber. a heat pump device including a compressor that compresses a refrigerant, a first interior heat exchanger provided inside a vehicle cabin, a second interior heat exchanger provided inside the vehicle cabin and upstream of the first interior heat exchanger in an airflow direction, an exterior heat exchanger provided outside the vehicle cabin, and first and second pressure reducing valves, the heat pump device being formed by connecting together the compressor, the first and second interior heat exchangers, the pressure reducing valves (52, 53) and the exterior heat exchanger via refrigerant piping; an interior air-conditioning unit which houses the first and second interior heat exchangers and which includes a blower that blows air-conditioning air to the first and second interior heat exchangers, the interior air-conditioning unit being configured to produce conditioned air and supply the conditioned air into the vehicle cabin; and an air-conditioning controller configured to control the heat pump device and the interior air-conditioning unit, wherein the air-conditioning controller makes the heat pump device operate while making a switch between multiple operation modes including a second dehumidification and heating operation mode in which the refrigerant discharged from the compressor is circulated through the first interior heat exchanger, the second pressure reducing valve, the exterior heat exchanger, and the second interior heat exchanger in this order so that the first interior heat exchanger functions as a radiator and the second interior heat exchanger functions as a heat absorber. characterized in that it includes a first dehumidification and heating operation mode in which a refrigerant discharged from the compressor is circulated through the first interior heat exchanger; the first pressure reducing valve, the second interior heat exchanger, and the exterior heat exchanger in this order so that the first interior heat exchanger functions as a radiator and the second interior heat exchanger functions as heat absorber.