Abstract: An interposer substrate of the present invention includes a planar substrate, and through hole wiring that is formed by filling a through hole that connects together a first main surface and a second main surface of this substrate with a conductor. When the through hole is viewed in a vertical cross-sectional view of the substrate, the through hole has a trapezoidal shape whose side walls are formed by an inside surface of the through hole, and two side faces of the trapezoid are not parallel to each other. The two side faces of the trapezoid are both inclined towards the same side relative to two perpendicular lines that are perpendicular to the first main surface or the second main surface at two apex points forming a top face or a bottom face of the trapezoid.