A wiring board comprising: a base including a front surface, a rear surface, and a side surface; a first metal plate joined with the front surface; a second metal plate joined with the rear surface; and a conductive line (50; 60) configured to electrically connect the first metal plate and the second metal plate, wherein the conductive line (50; 60) is arranged in an inner space defined by an inner wall surface of a base through hole formed in the base or an outer space located at an outer side of the side surface of the base, and the conductive line includes the first metal plate, the second metal plate, and a conductive material (60; 65) electrically connecting the first metal plate and the second metal plate, wherein at least one of the first metal plate and the second metal plate includes a joined portion (31, 41), which is joined with the base, and a bent portion (32, 42; 35, 45), which is bent and extended from the joined portion (31, 41) to cover the inner wall surface or the side surface, and the conductive material (60; 65) fills an inner side of the bent portion (32, 42; 35, 45), wherein the first metal plate includes a first joined portion, which serves as the joined portion (31, 41), and a first bent portion (32; 35), which serves as the bent portion (32, 42; 35, 45), and the first bent portion (32; 35) is bent toward the rear surface; and the second metal plate includes a second joined portion, which serves as the joined portion (31, 41), and a second bent portion (42; 45), which serves as the bent portion (32, 42; 35, 45), and the second bent portion (42; 45) is bent toward the front surface to cover the inner wall surface or the side surface together with the first bent portion (32; 35); characterized in that the conductive material (60; 65) fills the inner space or the outer space in which the second bent portion (42; 45) is arranged inwardly of the first bent portion (32; 35) within the inner space or outwardly of the first bent portion (32; 35) within the outer space to cover the first bent portion (32; 35) and the inner wall surface or the side surface. a base including a front surface, a rear surface, and a side surface; a first metal plate joined with the front surface; a second metal plate joined with the rear surface; and a conductive line (50; 60) configured to electrically connect the first metal plate and the second metal plate, wherein the conductive line (50; 60) is arranged in an inner space defined by an inner wall surface of a base through hole formed in the base or an outer space located at an outer side of the side surface of the base, and the conductive line includes the first metal plate, the second metal plate, and a conductive material (60; 65) electrically connecting the first metal plate and the second metal plate, wherein at least one of the first metal plate and the second metal plate includes a joined portion (31, 41), which is joined with the base, and a bent portion (32, 42; 35, 45), which is bent and extended from the joined portion (31, 41) to cover the inner wall surface or the side surface, and the conductive material (60; 65) fills an inner side of the bent portion (32, 42; 35, 45), wherein the first metal plate includes a first joined portion, which serves as the joined portion (31, 41), and a first bent portion (32; 35), which serves as the bent portion (32, 42; 35, 45), and the first bent portion (32; 35) is bent toward the rear surface; and the second metal plate includes a second joined portion, which serves as the joined portion (31, 41), and a second bent portion (42; 45), which serves as the bent portion (32, 42; 35, 45), and the second bent portion (42; 45) is bent toward the front surface to cover the inner wall surface or the side surface together with the first bent portion (32; 35); characterized in that the conductive material (60; 65) fills the inner space or the outer space in which the second bent portion (42; 45) is arranged inwardly of the first bent portion (32; 35) within the inner space or outwardly of the first bent portion (32; 35) within the outer space to cover the first bent portion (32; 35) and the inner wall surface or the side surface.