Abstract: A semiconductor package includes a semiconductor chip, an interconnection substrate having the semiconductor chip mounted on one surface of the interconnection substrate, and a package base having the interconnection substrate mounted on one surface of the package base. An optical transmission medium is provided on the package base at a location corresponding to an optical device provided on the interconnection substrate. On the other surface of the package base is provided a receptacle for making an optical connection between an optical fiber cable and the optical transmission medium. Signals are input and/or output via the optical fiber cable connected to the receptacle.