A heat exchanger that is supplied with air by a fan, the heat exchanger having a two-column structure and including an upwind heat exchanger element disposed upwind in a passing direction in which the air passes and a downwind heat exchanger element disposed downwind in the passing direction, each of the upwind heat exchanger element and the downwind heat exchanger element including: a fin (31, 32) that is plate-shaped; a first heat transfer tube extending through the fin (31, 32), the first heat transfer tube having a flat cross-section; and a second heat transfer tube extending through the fin (31, 32), the second heat transfer tube being disposed at a distance from the first heat transfer tube in a gravity direction, the second heat transfer tube having a flat cross-section, the first heat transfer tube having a first upwind end located upwind in the passing direction and a first downwind end located downwind in the passing direction, the second heat transfer tube having a second upwind end located upwind in the passing direction and a second downwind end located downwind in the passing direction, the fin having an upwind fin end located upwind in the passing direction and a downwind fin end located downwind in the passing direction, where the first upwind end and the second upwind end are connected by a first imaginary line and the first downwind end and the second downwind end are connected by a second imaginary line, the fin having an upwind fin region (161, 161') defined by the upwind fin end and the first imaginary line, a heat-transfer-tube region (163, 163') defined by the first imaginary line and the second imaginary line, and a downwind fin region (162, 162') defined by the second imaginary line and the downwind fin end, characterised in that in the upwind heat exchanger element, a dimension (A_1) of the upwind fin region being larger than a dimension (B_1) of the downwind fin region in the passing direction, a dimension (A_2) of the upwind fin region in the downwind heat exchanger element being equal in the passing direction to the dimension (B_1) of the downwind fin region in the upwind heat exchanger element, a dimension (B_2) of the downwind fin region in the downwind heat exchanger element being equal in the passing direction to the dimension (A_1) of the upwind fin region in the upwind heat exchanger element. a fin (31, 32) that is plate-shaped; a first heat transfer tube extending through the fin (31, 32), the first heat transfer tube having a flat cross-section; and a second heat transfer tube extending through the fin (31, 32), the second heat transfer tube being disposed at a distance from the first heat transfer tube in a gravity direction, the second heat transfer tube having a flat cross-section, the first heat transfer tube having a first upwind end located upwind in the passing direction and a first downwind end located downwind in the passing direction, the second heat transfer tube having a second upwind end located upwind in the passing direction and a second downwind end located downwind in the passing direction, the fin having an upwind fin end located upwind in the passing direction and a downwind fin end located downwind in the passing direction, where the first upwind end and the second upwind end are connected by a first imaginary line and the first downwind end and the second downwind end are connected by a second imaginary line, the fin having an upwind fin region (161, 161') defined by the upwind fin end and the first imaginary line, a heat-transfer-tube region (163, 163') defined by the first imaginary line and the second imaginary line, and a downwind fin region (162, 162') defined by the second imaginary line and the downwind fin end, characterised in that in the upwind heat exchanger element, a dimension (A_1) of the upwind fin region being larger than a dimension (B_1) of the downwind fin region in the passing direction, a dimension (A_2) of the upwind fin region in the downwind heat exchanger element being equal in the passing direction to the dimension (B_1) of the downwind fin region in the upwind heat exchanger element, a dimension (B_2) of the downwind fin region in the downwind heat exchanger element being equal in the passing direction to the dimension (A_1) of the upwind fin region in the upwind heat exchanger element.