A portable wireless device has no externally projecting part even when a card type functional medium has been therein inserted, and allows downsizing and obtaining high antenna performance.The portable wireless device includes a card slot (12) in a substrate (11) of a lower housing (10), and includes a slot cover (13) that can block an opening portion of the card slot (12). The slot cover (13) is integrally provided with a parasitic element (14). The parasitic element (14) is, when an SDIO card (100) is inserted, arranged so as to be in proximity substantially parallel with the antenna element (102) of the SDIO card (100), has an electrical length which is approximately one-half wavelength of a driving frequency of an RF circuit (101) of the SDIO card (100), and electromagnetically couples with the antenna element (102) to operate as a parasitic element.