A heat exchanger (10, 20), comprising: - a plurality of flat tubes arranged in a right-and-left direction orthogonal to a front-and-back direction, the front-and-back direction being an airflow direction of the heat exchanger; - a corrugated fin sandwiched by adjacent ones of the plurality of flat tubes and thermally connected to the adjacent ones of the plurality of flat tubes at each of apexes of the corrugated fin; - an inlet header connected to one end of each of the plurality of flat tubes; and - an outlet header connected to an other end of each of the plurality of flat tubes, - the heat exchanger (10, 20) being configured to serve as an evaporator for refrigerant flowing through the plurality of flat tubes, - a surface of the corrugated fin being to be adhered by at least one of dew condensation and frost, wherein - the plurality of flat tubes extends along an up-and-down direction of the heat exchanger (10, 20), - the corrugated fin includes a protruding portion protruding to a front side with respect to a front-side end portion of each of the plurality of flat tubes, - the protruding portion includes a plurality of first lug portions oriented obliquely to the front-and-back direction, the plurality of first lug portions being positioned on right and left sides of the protruding portion, - the corrugated fin further includes a second lug portion formed in the right-and-left direction at a part sandwiched by the adjacent ones of the plurality of flat tubes, wherein between the plurality of first lug portions positioned on the right and left sides, an interval is secured, the plurality of first lug portions each includes a slit formed in the protruding portion, one or more of the plurality of first lug portions are formed in a radial direction extending from one of the plurality of flat tubes toward a center portion of a front-side end portion of the protruding portion, and the heat exchanger (10, 20) includes passages for at least one of water which was the dew condensation and water which was the frost, the slit serving as one of the passages, surfaces of the plurality of flat tubes serving as another of the passages. - a plurality of flat tubes arranged in a right-and-left direction orthogonal to a front-and-back direction, the front-and-back direction being an airflow direction of the heat exchanger; - a corrugated fin sandwiched by adjacent ones of the plurality of flat tubes and thermally connected to the adjacent ones of the plurality of flat tubes at each of apexes of the corrugated fin; - an inlet header connected to one end of each of the plurality of flat tubes; and - an outlet header connected to an other end of each of the plurality of flat tubes, - the heat exchanger (10, 20) being configured to serve as an evaporator for refrigerant flowing through the plurality of flat tubes, - a surface of the corrugated fin being to be adhered by at least one of dew condensation and frost, wherein - the plurality of flat tubes extends along an up-and-down direction of the heat exchanger (10, 20), - the corrugated fin includes a protruding portion protruding to a front side with respect to a front-side end portion of each of the plurality of flat tubes, - the protruding portion includes a plurality of first lug portions oriented obliquely to the front-and-back direction, the plurality of first lug portions being positioned on right and left sides of the protruding portion, - the corrugated fin further includes a second lug portion formed in the right-and-left direction at a part sandwiched by the adjacent ones of the plurality of flat tubes, wherein the plurality of first lug portions each includes a slit formed in the protruding portion, one or more of the plurality of first lug portions are formed in a radial direction extending from one of the plurality of flat tubes toward a center portion of a front-side end portion of the protruding portion, and the heat exchanger (10, 20) includes passages for at least one of water which was the dew condensation and water which was the frost, the slit serving as one of the passages, surfaces of the plurality of flat tubes serving as another of the passages.