A method for manufacturing a fin for a heat exchanger includes the steps of forming an intermediate pre-formed plate, which has adjacent zigzag strips, by passing a flat plate material between a pair of first processing rollers, and forming a fin by passing the intermediate pre-formed plate between a pair of second processing rollers to bend the zigzag strips at a portion connecting adjacent zigzag strips. The fin includes a plurality of waving strips arranged adjacent to each other in the transverse direction, which are offset in the longitudinal direction. The adjacent waving strips are connected only between the flat portions of the waving strips at a connection length less than or equal to a plate thickness. The fin may be manufactured readily and inexpensively. A heat exchanger using the fin as an inner or outer fin may exhibit superior performance.