An air conditioner has an air conditioning case, a heat exchanger disposed in the air conditioning case to cool air therein, a drain pan disposed at a lower side of the heat exchanger to receive condensed water and the like, and a partition wall which is disposed between a lower surface of the heat exchanger and the drain pan to separate an air upstream side from an air downstream side in the air conditioning case. The drain pan has a drain hole, through which condensed water is discharged. An end portion of the partition wall intersects the drain hole and partitions the drain hole into the air upstream side and the air downstream side.