An RFID tag prevents reduction of communication characteristics due to mutual interference of RFID tags and enables to collectively read plural densely arranged RFID tags by a reader apparatus even when the plural RFID tags are in a densely arranged state. The RFID tag of the present invention is an RFID tag having an IC chip and a first antenna connected to the IC chip, provided with an impedance matching circuit for performing impedance matching between the IC chip and the first antenna, and arranged by stacking a conductor to cover the impedance matching circuit via an insulator base material.