PURPOSE: To provide a mobile position mounted on a vehicle for detecting the position of vehicle accurately by correcting the detected position automatically when the vehicle is running.

CONSTITUTION: Upon decision of the type of road when a vehicle is running, the image of specific road facility concerning the running road is recognized S20, S21. When the specific road facility is present, the position thereof is detected S22, $23. A series of variation in XY coordinates of a specific road facility and the running direction of vehicle at a moment passing through the specific road facility are then calculated thus updating the series of variation in XY coordinates of relevant road facility S24. When the series of positional coordinates of specific road facility can be determined uniquely based on the calculation results S25, S26, the position of specific road facility determined based on the series of positional coordinates is compared with that for which the vehicle detecting position is determined S27, S28. When the difference is within a predetermined value, the vehicle detecting position is corrected based on the recognized position of specific road facility S29, S30.