A heat exchanger includes a fin, the fin including a metal base and a porous anodized layer formed on the metal base. A surface of the porous anodized layer has a submicron-order uneven structure, the uneven structure including a plurality of recessed portions whose two-dimensional size viewed in a normal direction of the surface is more than 100 nm and less than 500 nm.本發明之熱交換器具有鰭片(50)，該鰭片(50)具有金屬基材(18Xr)、及形成於金屬基材上之多孔性陽極氧化層(14)，多孔性陽極氧化層之表面具有次微米級之凹凸結構，凹凸結構包含自表面之法線方向觀察時之二維大小超過100nm且未達500nm之複數個凹部(14Ap)、(14Bp)。
