In an interior air conditioning unit, a divided case is provided with a main water receiver, a main drain port, a side wall, a secondary drain port, a partition wall, a notch, a droplet reservoir, a path, and a tilted portion. The side wall, the secondary drain port, the notch, the droplet reservoir, the path, and the tilted portion are respectively located such that a condensate water flows out of the main water receiver and reaches the secondary drain port through the notch before a water surface of the condensate water reaches a fitting portion between the divided cases. According to the above-described configuration, the condensate water produced in the cooling heat exchanger can be certainly prevented from leaking through the fitting portion of the air conditioning case.