To obtain a detecting method in which the position of a vehicle running on a rail can be detected simply and precisely.

Gaps 1A which are formed usually between unit rails are utilized positively so that a rail 1 is not deformed due to a rise in a temperature or the like, the gaps 1A are detected by a sensor 4, and the number of the gaps 1A is counted. Then, an absolute position (a distance) from a certain reference point for a vehicle 2 is realized when the length of a unit rail is multiplied by the counted number of the gaps 1A. Thereby, the absolute position of the vehicle 2 can be detected simply and with high accuracy.