A multilayer wiring board includes a first dielectric layer, a high-frequency signal line formed on a first surface of the first dielectric layer, a ground layer formed on a second surface of the first dielectric layer, and a second dielectric layer covering part of the ground layer. The high-frequency signal line is electrically connectable to a center conductor of a coaxial structure. The second dielectric layer is spaced from an edge of the first dielectric layer to which the coaxial structure is to be connected, so that a ground exposure portion of the ground layer is exposed on the edge of the first dielectric layer. The ground layer is electrically connectable directly to an outer conductor of the coaxial structure at the ground exposure portion.