An air-conditioning unit includes an air-conditioning case and a heat exchanger. The heat exchanger includes a plurality of tubes and a header tank. The air-conditioning case includes a holder in which the header tank is held while being inserted therein. The holder includes a first rib and a plurality of second ribs for pressing a tank outer wall of the header tank toward an internal space of the header tank. The first rib extends in a tube stacking direction. The plurality of second ribs are each connected to the first rib, are formed to extend from the first rib away from the tubes, and are arranged side by side at a predetermined inter-rib spacing in the tube stacking direction. The inter-rib spacing is larger than a length of the second ribs extending from the first rib away from the tubes in a tube longitudinal direction.