A heat exchanger comprising: at least one heat transfer tube in which refrigerant flows; and a fin connected to the at least one heat transfer tube , the fin comprising: a first end connected to the heat transfer tube ; a flat portion continuing from the first end; and a second end continuing from the flat portion and located opposite to the first end with respect to the flat portion , the flat portion having a plurality of ribs in a line shape protruding from the flat portion , each rib comprising: a rib central portion located centrally between the first end and the second end; and a portion continuing from the rib central portion and formed to approach any one of the first end and the second end in a downstream direction of flowing air, each rib configured to guide condensation water on the fin towards one of the first end and second end of the fin; the flat portion having a plurality of louvers , the ribs and the louvers being arranged in the direction of flowing air, and characterised in that the plurality of louvers include louvers sandwiched by respective ribs of the plurality of ribs . at least one heat transfer tube in which refrigerant flows; and a fin connected to the at least one heat transfer tube , the fin comprising: a first end connected to the heat transfer tube ; a flat portion continuing from the first end; and a second end continuing from the flat portion and located opposite to the first end with respect to the flat portion , the flat portion having a plurality of ribs in a line shape protruding from the flat portion , each rib comprising: a rib central portion located centrally between the first end and the second end; and a portion continuing from the rib central portion and formed to approach any one of the first end and the second end in a downstream direction of flowing air, each rib configured to guide condensation water on the fin towards one of the first end and second end of the fin; the flat portion having a plurality of louvers , the ribs and the louvers being arranged in the direction of flowing air, and characterised in that the plurality of louvers include louvers sandwiched by respective ribs of the plurality of ribs . a first end connected to the heat transfer tube ; a flat portion continuing from the first end; and a second end continuing from the flat portion and located opposite to the first end with respect to the flat portion , the flat portion having a plurality of ribs in a line shape protruding from the flat portion , each rib comprising: a rib central portion located centrally between the first end and the second end; and a portion continuing from the rib central portion and formed to approach any one of the first end and the second end in a downstream direction of flowing air, a rib central portion located centrally between the first end and the second end; and a portion continuing from the rib central portion and formed to approach any one of the first end and the second end in a downstream direction of flowing air, each rib configured to guide condensation water on the fin towards one of the first end and second end of the fin; the flat portion having a plurality of louvers , the ribs and the louvers being arranged in the direction of flowing air, and characterised in that the plurality of louvers include louvers sandwiched by respective ribs of the plurality of ribs . <EOS>