The disclosed beam welding method involves: a metal-foil layering step of mounting a first metal foil and a second metal foil placed on the first metal foil on both a primary mounting surface and a secondary mounting surface of a support mount which are located adjacent to one another; a tight contact step of bringing the portions of the first and second metal foils mounted on the primary mounting surface into tight contact with one another along an imaginary welding line, with the portions of the first and second metal foils mounted on the secondary mounting surface being kept in a free state; and a welding-and-cutting step of cutting off the portions of the first and second metal foils mounted on the secondary mounting surface while welding together the portions of the first and second metal foils mounted on the primary mounting surface along the imaginary welding line by heating the first and second metal foils through convergent irradiation with an electron beam in a predetermined vacuum environment after the tight contact step.