There is provided a heat exchanger and a fin material for the heat exchanger that can suppress occurrence of hollow corrosion in a fin and hold cooling performance for a long period of time under a high corrosion environment. The heat exchanger includes an aluminum tube through which a working fluid circulates and an aluminum fin which is bonded to the tube. The fin has a region B around a grain boundary, and a region A around the region B. In the region B, 5.0×104 pieces/mm2 less of Al—Fe—Mn—Si based intermetallic compound, each of which has equivalent circle diameters of 0.1 to 2.5 μm, are present. In the region A, 5.0×104 pieces/mm2 to 1.0×107 pieces/mm2 of Al—Fe—Mn—Si based intermetallic compound, each of which has equivalent circle diameters of 0.1 to 2.5 μm, are present.