The method includes: a first step of forming, at a weld site of laminated layers of a metal foil, using a cutter having a longitudinal cross-sectional shape of a substantially V shape, a notch penetrating the laminated metal foil along a lamination direction and having a linear shape in a plan view, to cause the laminated layers of the metal foil closely contact each other in the lamination direction at an end of the notch; a second step of bringing a welding electrode into pressure contact with the weld site and then energizing the weld site via the welding electrode to perform resistance welding, and a forming step, performed between the first and second steps, of crushing the notch and a raised portion around the notch, to form a recess to thereby compress the notch and the raised portion in the lamination direction.