A crossed dual tag includes two tags each of which comprises, on one plane, a dipole antenna formed with conductors, a feeding part to which an IC chip is connected at the center of the dipole antenna, and a loop-shaped inductance part that is formed between the dipoles of the dipole antenna and connected to the dipoles of the dipole antenna in parallel with respect to the feeding part. The two tags are crossed at right angles, and stacked to contact as closely as possible so that the loops of the inductance parts overlap as wide as possible. A reader/writer of an RFID system sequentially switches the surface of a circular polarized wave of a wireless signal between forward and backward directions, and reads information written to a user memory area from the tag that responds more strongly.