A wiring board (1A, 1B), comprising: a first dielectric layer having a rectangular plate form; a ground conductor wiring which is positioned on a first face of the first dielectric layer and is connected to a ground potential, a first end portion of the ground conductor wiring extending to a first side (2a1) of the first face; a pair of signal conductor wirings which is positioned on the first face of the first dielectric layer and carries out signal transmission, the pair of signal conductor wirings being positioned along the ground conductor wiring keeping a predetermined distance from the ground conductor wiring on both sides in a width direction of the ground conductor wiring, first end portions of the pair of signal conductor wirings extending to the first side (2a1) of the first face; a ground conductor layer which is positioned on a second face of the first dielectric layer and is connected to a ground potential, a region of the ground conductor layer where the first end portions of the pair of signal conductor wirings are positioned in plan view being cut away inwardly from a first side (2b1) of the second face opposing the first side (2a1) of the first face; and a second dielectric layer having a rectangular plate form, the second dielectric layer being positioned on a side of the ground conductor layer opposite to the first dielectric layer; wherein the second dielectric layer has a first side face (6a1) parallel to a plane including the first side (2a1) of the first face and the first side (2b1) of the second face of the first dielectric layer, and the second dielectric layer further has at least one cutaway portion being cut away from a side of the first side face (6a1) and, characterized by in plan view, the one cutaway portion being located to cover both a region of the second dielectric layer where the first end portions of the pair of signal conductor wirings are positioned and a region of the second dielectric layer where the first end portion of the ground conductor wiring is positioned. a first dielectric layer having a rectangular plate form; a ground conductor wiring which is positioned on a first face of the first dielectric layer and is connected to a ground potential, a first end portion of the ground conductor wiring extending to a first side (2a1) of the first face; a pair of signal conductor wirings which is positioned on the first face of the first dielectric layer and carries out signal transmission, the pair of signal conductor wirings being positioned along the ground conductor wiring keeping a predetermined distance from the ground conductor wiring on both sides in a width direction of the ground conductor wiring, first end portions of the pair of signal conductor wirings extending to the first side (2a1) of the first face; a ground conductor layer which is positioned on a second face of the first dielectric layer and is connected to a ground potential, a region of the ground conductor layer where the first end portions of the pair of signal conductor wirings are positioned in plan view being cut away inwardly from a first side (2b1) of the second face opposing the first side (2a1) of the first face; and a second dielectric layer having a rectangular plate form, the second dielectric layer being positioned on a side of the ground conductor layer opposite to the first dielectric layer; wherein the second dielectric layer has a first side face (6a1) parallel to a plane including the first side (2a1) of the first face and the first side (2b1) of the second face of the first dielectric layer, and the second dielectric layer further has at least one cutaway portion being cut away from a side of the first side face (6a1) and, characterized by in plan view, the one cutaway portion being located to cover both a region of the second dielectric layer where the first end portions of the pair of signal conductor wirings are positioned and a region of the second dielectric layer where the first end portion of the ground conductor wiring is positioned.