A semiconductor device comprising a wiring member with which a semiconductor chip is electrically connected including: a first wiring layer having a plurality of first conductive patterns; a second wiring layer arranged next to the first wiring layer in a thickness direction of the wiring member, and having a second conductive pattern; and a third wiring layer arranged next to the second wiring layer in the thickness direction of the wiring member, and having a third conductive pattern. Here, in plan view, a first opening portion of each of two, which are arranged next to each other, of a plurality of first opening portions each penetrating through the second conductive pattern is overlapped with a pair of differential signal wirings contained in plurality of first conductive patterns, and is overlapped with two or more of a plurality of second opening portions each penetrating through the third conductive pattern.