A coupling system (1, 101, 201, 301, 401, 501, 601, 701) configured to couple a first plate made of a first metal and a second plate made of a second metal to each other, the coupling device (1, 101, 201, 301, 401, 501, 601, 701) comprising: (a) a coupling member (50, 150, 250, 350, 450, 550, 650, 750); (b) a first electrode and a second electrode; (c) a power source connected to the first electrode and the second electrode; (d) a driver configured to move the first electrode and the second electrode relative to the coupling member (50, 150, 250, 350, 450, 550, 650, 750), the first plate, and the second plate; and (e) a controller configured to control the power source and the driver to electrify the coupling member (50, 150, 250, 350, 450, 550, 650, 750), the first plate, and the second plate while controlling the first electrode and the second electrode to apply pressure to the coupling member (50, 150, 250, 350, 450, 550, 650, 750), the first plate, and the second plate, wherein the coupling member (50, 150, 250, 350, 450, 550, 650, 750) is made of a third metal identical to the second metal, wherein the first metal has a melting point lower than a melting point of the second metal and a melting point of the third metal, wherein the coupling member (50, 150, 250, 350, 450, 550, 650, 750) comprises a body, a pilot portion (53, 153, 353, 553, 653, 753) provided at a center of a flat surface (51 a) of the body and protruding in an extending direction, and a ring-shaped wall (58, 258, 358, 458, 658) provided along an outer circumference of the flat surface, wherein the pilot portion (53, 153, 353, 553, 653, 753) is solid, wherein the pilot portion (53, 153, 353, 553, 653, 753), the body, and the ring-shaped wall (58, 258, 358, 458, 658) define a groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a), characterized by the groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a) having a first volume equal to or greater than a second volume of a protrusion of the pilot portion (53, 153, 353, 553, 653, 753), the protrusion protruding from an open surface (50b, 150b, 250b, 350b, 450b, 550b, 650b) of the groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a) in an outward direction away from the groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a). (a) a coupling member (50, 150, 250, 350, 450, 550, 650, 750); (b) a first electrode and a second electrode; (c) a power source connected to the first electrode and the second electrode; (d) a driver configured to move the first electrode and the second electrode relative to the coupling member (50, 150, 250, 350, 450, 550, 650, 750), the first plate, and the second plate; and (e) a controller configured to control the power source and the driver to electrify the coupling member (50, 150, 250, 350, 450, 550, 650, 750), the first plate, and the second plate while controlling the first electrode and the second electrode to apply pressure to the coupling member (50, 150, 250, 350, 450, 550, 650, 750), the first plate, and the second plate, wherein the coupling member (50, 150, 250, 350, 450, 550, 650, 750) is made of a third metal identical to the second metal, wherein the first metal has a melting point lower than a melting point of the second metal and a melting point of the third metal, wherein the coupling member (50, 150, 250, 350, 450, 550, 650, 750) comprises a body, a pilot portion (53, 153, 353, 553, 653, 753) provided at a center of a flat surface (51 a) of the body and protruding in an extending direction, and a ring-shaped wall (58, 258, 358, 458, 658) provided along an outer circumference of the flat surface, a body, a pilot portion (53, 153, 353, 553, 653, 753) provided at a center of a flat surface (51 a) of the body and protruding in an extending direction, and a ring-shaped wall (58, 258, 358, 458, 658) provided along an outer circumference of the flat surface, wherein the pilot portion (53, 153, 353, 553, 653, 753) is solid, wherein the pilot portion (53, 153, 353, 553, 653, 753), the body, and the ring-shaped wall (58, 258, 358, 458, 658) define a groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a), characterized by the groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a) having a first volume equal to or greater than a second volume of a protrusion of the pilot portion (53, 153, 353, 553, 653, 753), the protrusion protruding from an open surface (50b, 150b, 250b, 350b, 450b, 550b, 650b) of the groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a) in an outward direction away from the groove space (50a, 150a, 250a, 350a, 450a, 550a, 650a).