The purpose of the present invention is to provide: a heat exchanger in which an insertion hole of a header and an end of the heat exchange member can be joined appropriately; a heat exchanger unit; a refrigeration cycle apparatus; and a heat exchange member manufacturing method. A heat exchanger, a heat exchanger unit, a refrigeration cycle apparatus, and a heat exchange member manufacturing method according to the present invention involve being provided with a heat exchange member extending in a first direction, and headers having connected thereto ends, in the first direction, of the heat exchange member, wherein: the heat exchange member is provided with at least one heat-transfer pipe extending in the first direction, and fins each formed at a portion of an edge of said at least one heat-transfer pipe in a second direction intersecting with the first direction; the fins are each provided to a fin installation part at at least a portion other than the ends of the heat exchange member; and the width dimension, in the second direction, of said at least one heat-transfer pipe at the ends is smaller than the width dimension, in the second direction, of said at least one heat-transfer pipe in the fin installation parts.
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