A fin according to the present disclosure is a corrugated fin formed of a metal plate by bending into a corrugated shape, and the corrugated fin includes peak portions extending in a first direction, valley portions extending in the first direction, and inclined portions connecting the peak portions and the valley portions adjacent to each other. The peak portions and the valley portions are alternately arranged in a second direction perpendicular to the first direction, and a thickness of the metal plate at each apex of the peak portions and the valley portions is larger than a thickness of the inclined portions of the metal plate.