A mobile wireless device including: first housing, a second housing, a signal line electrically connecting a circuit of the first housing and a circuit of the second housing, and a connection portion for connecting the first housing and the second housing so that they can be opened and closed, wherein ends of the housings have openings communicating with interiors of the housings and through which the signal line passed, the second housing houses an electronic circuit including a wireless unit, the electronic circuit has one end of the signal line connected to it, the first housing houses a circuit board including a reference potential layer, and the circuit board has the other and of the signal line connected to it, a conductive part is arranged from the opening of the first housing up to a position of the circuit board where the signal line is connected, and the conductive part is electrically connected to the reference potential layer of the circuit board.