Provided are corrugated fins that have high heat transfer performance and do not cause clogging even in a gaseous environment in which particulate matter such as dust is present. Each wall surface 3 of corrugated fins comprises alternating parallel ridges 4 and furrows 5 with an angle of inclination of 10-60°. Defining Wh as the height of the ridges and furrows, Wp as the pitch of the ridges and furrows, Pf as the pitch of the corrugated fins, and Tf as the thickness of the fins, the following conditions hold. Wh ≦ 0.3674 ⋅ Wp + 1.893 ⋅ Tf − 0.1584 , 0.088 Wh − Tf / Pf 0.342 , and a ⋅ Wp 2 + b ⋅ Wp + c Wh , where a = 0.004 ⋅ Pf 2 − 0.0696 ⋅ Pf + 0.3642 , b = − 0.0036 ⋅ Pf 2 + 0.0625 ⋅ Pf − 0.5752 , and c = 0.0007 ⋅ Pf 2 + 0.1041 ⋅ Pf + 0.2333.