The present invention has an object of attaining further miniaturization and reducing the thickness of a portable wireless device with a built-in antenna. The cellular telephone device 1 according to the one embodiment of the present invention includes a case body 60 having a first case portion 62 which is arranged so as to cover the electronic components, along with being electrically conductive to the reference potential pattern, and a nonconductive second case portion 64 arranged to be continuous to the first case portion 62 along with being arranged in the outer periphery of the circuit substrate 70. In the portion that is arranged to be layered in the second case portion 64 in a flexible wiring substrate 50, an antenna element 66 is arranged.