To provide a communication method of an RFID tag capable of quickly processing a plurality of RFID tags, and to provide a read-write machine for the RFID tag used for the method.

In the communication method of the RFID tag, a frequency range having prescribed width with a prescribed communication frequency as the center is divided into a plurality of frequency bands (3a, 3b, 3c), and each of the plurality of frequency bands (3a, 3b, 3c) is used for the communication 4 between the read-write machine 1 and one RFID tag (2a, 2b, or 2c). The read-write machine for the RFID tag used for the communication method simultaneously processes signals at a plurality of frequency bands, and superposes the signals for transmission and reception.