A cable comprising: two metal conductor wires (11, 12); and a coating (20, 70, 80) that is made of a transparent or translucent material, has a width which is larger than a height, covers the two metal conductor wires (11, 12) in a state of being arranged in parallel at an interval, and is shaped in a manner that a bottom surface (22, 74) existing along a direction substantially parallel to a direction between the two metal conductor wires (11, 12) is a plane, an upper surface (21, 81) opposing the bottom surface (22, 74) has a curved surface with a convex cross section, and two opposing side face parts (23, 24, 72, 73) exist which extend between the bottom surface (22, 74) and the upper surface (21, 81), wherein the upper surface (21, 81) comprises two small radius shoulder parts (21a, 21b, 81a, 81b) in contact with the side face parts (23, 24, 72, 73), wherein the curved surface extends between the two shoulder parts (21a, 21b, 81a, 81b) and has a large radius, and wherein one of the two metal conductor wires (11, 12) is arranged at a close position to one of the two side face parts (23, 24, 72, 73), and the other one of the two metal conductor wires (11, 12) is arranged at a close position to the other one of the two side face parts (23, 24, 72, 73), characterized in that the two opposing side face parts (23, 24, 72, 73) are planes, and in that radii of curvatures of the two shoulder parts (21a, 21b, 81a, 81b) are smaller than a radius of curvature of the curved surface, wherein a light beam incident on the curved surface from a direction perpendicular to a plane at least including the two metal conductor wires (11, 12) is refracted by the curved surface and does not pass through the two metal conductor wires, wherein the curvature of the curved surface is gradually changed so that the same curvature does not continue. two metal conductor wires (11, 12); and a coating (20, 70, 80) that is made of a transparent or translucent material, has a width which is larger than a height, covers the two metal conductor wires (11, 12) in a state of being arranged in parallel at an interval, and is shaped in a manner that a bottom surface (22, 74) existing along a direction substantially parallel to a direction between the two metal conductor wires (11, 12) is a plane, an upper surface (21, 81) opposing the bottom surface (22, 74) has a curved surface with a convex cross section, and two opposing side face parts (23, 24, 72, 73) exist which extend between the bottom surface (22, 74) and the upper surface (21, 81), wherein the upper surface (21, 81) comprises two small radius shoulder parts (21a, 21b, 81a, 81b) in contact with the side face parts (23, 24, 72, 73), wherein the curved surface extends between the two shoulder parts (21a, 21b, 81a, 81b) and has a large radius, and wherein one of the two metal conductor wires (11, 12) is arranged at a close position to one of the two side face parts (23, 24, 72, 73), and the other one of the two metal conductor wires (11, 12) is arranged at a close position to the other one of the two side face parts (23, 24, 72, 73), characterized in that the two opposing side face parts (23, 24, 72, 73) are planes, and in that radii of curvatures of the two shoulder parts (21a, 21b, 81a, 81b) are smaller than a radius of curvature of the curved surface, wherein a light beam incident on the curved surface from a direction perpendicular to a plane at least including the two metal conductor wires (11, 12) is refracted by the curved surface and does not pass through the two metal conductor wires, wherein the curvature of the curved surface is gradually changed so that the same curvature does not continue.