A soft magnetic member which is formed by a composite of an organic object to satisfy a predetermined relationship with an antenna area, a circumference length, and a magnetic transmission ratio and a conductive member are provided between an antenna coil which is formed by at least one loop and a metal surface of the conductive member such as a metal casing. The magnetic flux which invades into the conductive object is blocked by the soft magnetic member and the conductive member so as to restrict the influence thereof.