We have developed and implemented a system that measures the body fit of completed vehicles automatically and with high precision on a continuously moving assembly-line conveyor. The system uses a robot that is synchronized to the conveyor movement to position a vision sensor at specified measurement points. The sensor measures clearance and levelness between adjacent body panel parts (e.g. between hood and fender). The vision sensor employs a slit beam laser and a CCD camera. The sensor's optical system, particularly the thickness of the slit beam, was modified to prevent the color of the object surface from influencing the measurement. A new algorithm was developed for higher measurement precision. Vehicles on an assembly line vary in position and orientation on the conveyor, so we developed a device to measure the vehicle position and orientation precisely in three dimensions.