Abstract: A coupling device couples, using a coupling member, a first plate of a first metal to a second plate of a second metal. A power source is connected to first and second electrodes. A driver moves the first and second electrodes relative to the coupling member and the first and second plates. A controller controls the power source and the driver to electrify the coupling member and the first and second plates under pressure. The coupling member includes a third metal approximately identical to the second metal. The first metal has a melting point lower than melting points of the second and third metals. The coupling member includes a pilot portion that is located about a center of a flat surface of a body of the coupling member and that protrudes in an extending direction. The flat surface has discharge grooves radially extending from the pilot portion.