A heat exchanger, comprising: a plurality of flat tubes arranged one above another such that flat surfaces thereof face each other; and a plurality of vertically extending, plate-like fins arranged in an extension direction of the flat tubes, wherein each of the fins includes a plurality of intermediate plates arranged one above another and dividing a space between adjacent ones of the flat tubes into air passages, a plurality of tube insertion portions each provided between vertically adjacent ones of the intermediate plates, with an upwind side thereof being open such that a corresponding one of the flat tubes is inserted therein, a vertically extending downwind plate that is continuous with downwind ends of the plurality of intermediate plates arranged one above another, and a plurality of upwind plates extending further toward an upwind side than the flat tubes from upwind side ends of the intermediate plates, and each of the upwind plates is provided with at least one upwind side heat-transfer portion (81, 91, 92, 95) which projects in a thickness direction of the fins, and characterised in that the upwind side heat transfer portion includes a first upwind side heat transfer portion formed by making each of the fins protrude toward the air passages to have an inverted V-shaped portion, and second and third upwind side heat transfer portions (91, 92) which are provided at areas on the upper and lower sides of the first upwind side heat transfer portion respectively, project toward the air passage and extend horizontally in an air passage direction to lie across the upwind plate and the intermediate plate. a plurality of flat tubes arranged one above another such that flat surfaces thereof face each other; and a plurality of vertically extending, plate-like fins arranged in an extension direction of the flat tubes, wherein each of the fins includes a plurality of intermediate plates arranged one above another and dividing a space between adjacent ones of the flat tubes into air passages, a plurality of tube insertion portions each provided between vertically adjacent ones of the intermediate plates, with an upwind side thereof being open such that a corresponding one of the flat tubes is inserted therein, a vertically extending downwind plate that is continuous with downwind ends of the plurality of intermediate plates arranged one above another, and a plurality of intermediate plates arranged one above another and dividing a space between adjacent ones of the flat tubes into air passages, a plurality of tube insertion portions each provided between vertically adjacent ones of the intermediate plates, with an upwind side thereof being open such that a corresponding one of the flat tubes is inserted therein, a vertically extending downwind plate that is continuous with downwind ends of the plurality of intermediate plates arranged one above another, and a plurality of upwind plates extending further toward an upwind side than the flat tubes from upwind side ends of the intermediate plates, and each of the upwind plates is provided with at least one upwind side heat-transfer portion (81, 91, 92, 95) which projects in a thickness direction of the fins, and characterised in that the upwind side heat transfer portion includes a first upwind side heat transfer portion formed by making each of the fins protrude toward the air passages to have an inverted V-shaped portion, and second and third upwind side heat transfer portions (91, 92) which are provided at areas on the upper and lower sides of the first upwind side heat transfer portion respectively, project toward the air passage and extend horizontally in an air passage direction to lie across the upwind plate and the intermediate plate.