PURPOSE: To cope with the car model change in a short time by using a welding robot and a general purpose hemming press unit.

CONSTITUTION: A door assembly line is provided with a parts set at its starting end, temporary welding stage 11, augmented welding state 12, marriage process 13, hemming process 14, after-hem welding process 15, and outer panel storage 17 connected to the marriage process through a labeler process 16, and individual processes are connected together with a conveyor unit 18. In case of a model change, only the jig of a multi-spot welding equipment in the temporary welding process 11 is required for new installation, because the augmented welding process 12 and after-hem welding process 15 can be coped with by changing the teaching of the welding robot and the hemming process 14 can be coped with by replacing a press die.