A navigation device changes a position determination accuracy of a receiver for satellite navigation to a higher accuracy in the following cases: when the subject vehicle approaches a destination, the subject vehicle runs on a road not described in map information, when the subject vehicle approaches an intersection at which the road is branched at a narrow angle within a predetermined distance, when the subject vehicle is running on a narrow street, when the subject vehicle is running on one of adjacent parallel roads, when self-contained sensors are calibrated, and other like occasions. In the other cases, the navigation device changes the position determination accuracy of the receiver to a low accuracy. When the receiver is caused to execute low-accuracy position determination, power supply to receiver's operation required only for high-accuracy position determination is prohibited.