A semiconductor device includes a substrate; a holding member located on the substrate, the holding member including a module placement part and an opening arranged in a first direction; an optical module located in the module placement part and mounted on the substrate; and an optical fiber passing through the opening, the optical fiber being connected with the optical module. The holding member includes a first corner part and a second corner part. The opening is between the first corner part and the second corner part in a direction crossing the first direction. The first corner part and the second corner part are beveled.