A subject of the present invention is to provide an antenna unit and a portable radio device capable of attaining a wider bandwidth and a lower SAR.In the present invention, an antenna element (12) that has an effective length corresponding to a half wavelength of a transmitting frequency and a parasitic element (13) that has an effective length corresponding to a half wavelength of a receiving frequency are provided, an antenna current is induced in the antenna element (12) at the transmitting frequency upon transmitting a radio wave in a predetermined transmitting frequency band, and another antenna current is induced in the parasitic element (13) by a spatial coupling between the antenna element (12) and the parasitic element (13) at the receiving frequency upon receiving the radio wave in a predetermined receiving frequency band, whereby peak points in an antenna current distribution are scattered into two points. Accordingly, a wider bandwidth can be obtained without addition of a matching circuit and also expansion of a parts packaging space on a board and reduction in the number of packaged parts can be achieved.