PURPOSE: When producing cars of different specification on a common line, to facilitate the relative work between the indication and the reading of the information while to increase the density of a car type information, by applying a paint containing a ferromagnetic material on a set part and magnetizing to store the car type information.

CONSTITUTION: The upstream side of a floor main line 1 is applied with a paint containing a ferromagnetic material while a painting device 30 is provided to store magnetically. While part feeders 50, 70, 90 for automatically reading the information stored in the magnetic member then automatically selecting and carrying the assembled part are provided on the floor main line 1, body main line 2 and a metal line 4. A point device 100 for reading the information to switch the line is provided between the lines 1 and 2 while an automatic stamping device 110 for reading the information to stamp the body number is provided between the line 2 and a special work line 3. A special work indicator 130 for reading the information to tell the special body work to the worker is also provided on the line 3.