PURPOSE: To improve the precision of detection by allowing the coil surface of a subloop coil to overlap the coil surface of a main loop coil so as to include a part of the coil side to form the coil surface of the main loop coil, and providing these coil surfaces in a separate manner with the clearance in the advancing direction of a railway vehicle.

CONSTITUTION: A main loop coil 11 and subloop coils 12, 13 form a single coil surface. Because they are not twisted in the middle way, the induced electromotive force generated by the electromagnetic coupling to an induction loop coil 22 is not canceled. The information wave detecting signals S21-S23 of the specified level are obtained accompanied by the movement of a vehicle 3. The coil surfaces of the subloop coils 12, 13 overlap the coil surface of the main loop coil 11, and provided in a separate manner with the clearance therebetween in the advancing direction (a) of the vehicle 3. The main loop coil 11 and the subloop coils 12, 13 are successively connected to the induction loop coil 22 accompanied with the advancement of the vehicle 3. The vehicle position detecting signal S3 of three-bit is generated to increase the information on the vehicle position, resulting in the improvement of the precision of detection.