FIN FOR HEAT EXCHANGER

This fin comprises a plate-shaped substrate part (10) having a heat transfer tube passing part, which is a circular shape centered on a central axis C and through which a heat transfer tube passes, and a louver part at which a first slit is formed by a first louver (21). The louver part has a flat section (16), the first louver (21) that is provided on the downstream side of the flat section (16) and protrudes more in the Z-axis direction than the flat section (16), and a second louver (22) that is provided on the downstream side of the first louver (21). The second louver (22) has a linear part (22b) at which the shape of the cross-section thereof when cut in the XZ plane is linear, a second louver upstream part (22a) bending obliquely in the upstream direction from the upstream end of the linear part (22b) and extending linearly, and a second louver downstream part (22c) bending obliquely in the downstream direction from the downstream end of the linear part (22b) and extending linearly. The linear part (22b) is disposed so as to overlap with the heat transfer tube passing part when viewing the cross-section.