To provide a manufacturing method for manufacturing a fin having projected and recessed lines that are juxtaposed with good heat transfer coefficient easily at low cost and a heat exchanger using it.

A plate material is passed through the first working roll, and two or more rows of zigzag lines are arranged side by side. An intermediate working plate, in which the zigzag lines adjacent to each other are offset by half a pitch in the direction in which the plate material travels to be connected at the intermediate point of each oblique plate, is formed. After that, the intermediate working plate is passed through the second working roll, and is bent at the connected points of the zigzag lines adjacent to each other. Two or more rows of serial projected and recessed lines 25, in which the first flat part 21, the first oblique plate part 22 extending at the first bevel to the first flat part, the second flat part 23 extending parallel to the first flat part to the first oblique plate part and the second oblique plate part 24 extending at the second bevel to the second flat part are repeated in this order, are arranged side by side, and the locations of the adjacent projected and recessed lines are offset in the extending direction. Moreover, the first and second flat parts are connected, and a fin with the side T of the connected part that is the plate thickness (t) of the projected and recessed line or smaller is formed.