An interior unit includes a discharge water passage communicating with a drainage port and having a first space portion in which water inside an air conditioning casing flows down from a guide opening portion, and an upward wall portion and a downward wall portion which constitute a partition wall separating between the discharge water passage and a second space portion adjacent to the discharge water passage and preventing the water falling in the discharge water passage from flowing into the second space portion. A prevention wall extending upward from a bottom wall portion in the second space portion is provided, and an upper end of the prevention wall is higher than a position of a fixation portion in which the first casing member and the second casing member are fixed with each other.