To provide a wireless data carrier system in which sufficient sensitivity can be obtained even when a transmitter/receiver and a responder are separated from each other, the responder is small-sized and further, signal processing can be performed even when there are a plurality of responses to one inquiry.

A wireless data carrier system includes a transmitter 10 having a transmission antenna 13, and a receiver 30 which is disposed in the magnetic field area of the transmission antenna 13 and has a receiver antenna 31, and a responder 2 having a resonance circuit for a radio wave oscillated by the transmission antenna 13 and a switch circuit for giving a load modulation signal to the resonance circuit in accordance with data held by itself, passes or is disposed in the middle of the magnetic field area from the transmission antenna 13 to the reception antenna 31.