Provided is a welded structure in which a voltage detection terminal (21) plated with tin and a busbar (25) plated with nickel are welded, the busbar (25) having a thickness greater than that of the voltage detection terminal (21) and being formed with a protrusion (25c) which protrudes toward the voltage detection terminal (21) on a part of a surface facing the voltage detection terminal (21) at the time of being welded with the voltage detection terminal (21).