To accurately determine the three-dimensional shape of a road.

During running of an observation car 10 on a road, a car-carried hybrid position measuring unit 64 measures the latitude, the longitude and the height of a running trace of the car 10. In parallel, a car-carried video camera 20 takes images of the road and a picture processor 66 extracts white lines at both sides of the road to obtain the distance between the position of the car 10 and the center point of the road, based on the white lines, and calculates the latitude, the longitude and the height of the load center point, using the latitude, the longitude and the height of the travel trace, the distance between the observation car position and the road center point, and the yaw angle and the roll angle from a car-carried three-axis angle sensor 40. It obtains a three- dimensional shape of the road center line from the result and obtains a gradient in the road width direction from the roll angle to determine the latitude, the longitude and the height of an optional position on the road.