PURPOSE: To form the parting line of a sill part to a definite linear shape without masking, by floating a skid which supports a body from a carriage during painting and maintaining the same at a specified height.

CONSTITUTION: A skid 2 which supports a body 1 is placed on a carriage 5, and is propelled by a chain device 9 and is moved to the set position of a levelizer 13. When the skid is ridden over the levelizer 13 by a ski member 12, the skid 2 floats apart by a distance (d) from the carriage 5, but the length of the perpendicular surface of a guide member 14 in contact with the end part of the skid is longer than the distance (d); therefore, the skid 2 is still propelled. Since the skid 2 is propelled on the levelizer 13 in this stage, the height from the floor surface is made constant and the parting line in the sill part 1a of the body 1 is maintained at a specified height. Here, an automatic spray painting machine 15 is moved in the direction opposite from the advance direction of the skid while the specified height is maintained.