To remove a disturbance wave caused by a received signal of the other track by clearing a state variable of a digital filter of a received signal received from one track circuit, and detecting a train by performing digital signal processing on a signal received from the other one track circuit.

When a train detecting signal is switched to a track 2T from a track 1T, a state variable of a train detecting digital filter of the track 1T is cleared (b). Thus, a received signal of the track 2T is analyzed on the basis of only a received signal of the track 2T, that is, train is detected by removing a disturbance wave of a residual receiving level of the other track (c). Similarly, a train detecting signal is switched to a track 3T, and when the train is detected, a received signal of the track 3T can be analyzed on the basis of only the received signal of the track 3T. Even when the train detecting signal is switched to the track 1T, a train of the track 1T can be detected without being influenced by the track 3T.