配线基板具备绝缘基体、通孔、上面侧连接盘导体、下面侧连接盘导体及通孔导体。绝缘基体在第1、2绝缘层之间含有玻璃钢。通孔随着从上面向绝缘基体的内部而缩小直径，直径在玻璃钢的位置成为最小，随着从玻璃钢向下面而扩大直径。上面侧连接盘导体及下面侧连接盘导体分别覆盖通孔的上面侧及下面侧的开口部。通孔导体形成于通孔内。通孔的上面侧的开口部直径大于下面侧的开口部直径，上面侧连接盘导体的直径大于下面侧连接盘导体的直径。

Provided is a wiring substrate comprising an insulating base, a through hole, an upper surface-side land conductor, a lower surface-side land conductor and a through hole conductor. The insulating base comprises glass fibers between a first and a second insulating layer. The diameter of the through hole decreases from the upper surface toward the interior of the insulating body, is smallest at the position of the glass fibers, and becomes increasingly wider from the glass fibers toward the bottom surface. The upper surface-side land conductor and the lower surface-side land conductor respectively cover the opening of the through hole at the upper surface side and the lower surface side. The through hole conductor is formed within the through hole. The diameter of the upper surface-side opening of the through hole is larger than the diameter of the lower surface-side opening of the through hole and the diameter of the upper surface-side land conductor is larger than the diameter of the lower surface-side land conductor.