A heat exchanger (1) includes a heat transfer tube (3, 4). The heat transfer tube includes a first tube portion (3), and a plurality of second tube portions (4) connected in parallel with each other with respect to the first tube portion. The first tube portion has a first inner circumferential surface (30), and a plurality of first grooves (31) recessed relative to the first inner circumferential surface and arranged side by side in a circumferential direction of the heat transfer tube. The plurality of second tube portions each have a second inner circumferential surface (40), and a plurality of second grooves (41) recessed relative to the second inner circumferential surface and arranged side by side in the circumferential direction. The plurality of first grooves are less than the plurality of second grooves in at least one of a number of grooves, a depth of each groove, and a lead angle of each groove.
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