Abstract: A magnetic apparatus for detecting a position of a vehicle, capable of detecting a lateral deviating distance of a vehicle over a lateral deviation width with a high accuracy and at a high speed, wherein a magnetic field component in the direction of advance of the vehicle is detected; or more preferably a three dimensional magnetic sensor (1), which comprises a magnetic sensor element for the direction of advance of the vehicle, and magnetic sensor elements for two directions crossing the first-mentioned direction and provided additionally, is used, whereby it becomes possible to heighten a center retaining capability of the vehicle, widen a lateral deviating distance detecting range around four times from around 25 cm to around 1 m, and detect a magnetic marker (3) reliably even when disturbance magnetic field exerts influence upon this detection operation to thereby start center side guidance reliably.