In an RFID system including RFID tags each incorporating a sensor, accuracy of measurement by the sensor can be improved. For example, when measurements are performed several times by using RFID tags each incorporating a sensor unit, generation of a carrier directed from an RFID reader/writer to the RFID tags is stopped for a predetermined period every time when a measurement ends. By this means, the chip temperature of the RFID tag increased due to power consumption in each measurement can be reduced to, for example, ambient temperature every time when a measurement ends. Therefore, an error in measurement by the sensor unit can be reduced, thereby achieving accurate measurement.