There is a problem related to radio wave interference, e.g. the shade of radio wave of a radio IC tag, when a plurality of radio IC tags are present in a region of electromagnetic wave. When a plurality of antennas each having a large area are present in the vicinity of the radio IC tag, the radio IC tag easily receives the affect of an antenna conductor. In a plurality of radio IC tags present in a radio wave area, width of the antenna conductor of the radio IC tag is set at 1.0 mm or less. Furthermore, in order to realize an antenna conductor having a small width, an IC tag chip of both side electrode structure having electrodes on the front surface and rear surface of a chip is sandwiched between antennas.