A heat exchanger includes a plurality of fins stacked with a predetermined fin pitch between them, and a plurality of heat transfer tubes which extend through the fins in the stack direction and have a flat cross-sectional shape, wherein the fins have a plurality of notches in a shape corresponding to the cross-sectional shape of the heat transfer tube on an end portion in the longitudinal direction, a collar is formed on an edge of the plurality of notches, the heat transfer tubes are inserted into the notches, a fin pitch between a portion of the plurality of fins is larger than a fin pitch between the other portion of the fins, and the larger fin pitch is larger than at least the height of the collar.