PURPOSE: To improve a flash feeling of appearance, while contriving assembly work of a car body, by connecting a roof side rail outer panel to the end part of a roof panel and performing subassembly thereafter connecting a roof side rail inner panel to this outer panel.

CONSTITUTION: In assembly of an automobile for its roof side part, first a bottom end flange 2b of an outer panel 2 in a roof side rail 1 is connected to an extension end part 7a of a roof panel 7 by spot welding in a part W1, and subassembly is performed of both the roof panel and outer panel. Subsequently, these subassembled roof panel 7 and outer panel 2 in the roof side rail 1 are dropped to its inner panel 4 as shown by an arrow head. Thereafter, both upper and bottom end flanges 2a, 2b of the outer panel 2 in the roof side rail 1 and both upper and bottom end flanges 4a, 4b of the inner panel 4 are connected by spot welding in parts W2, W3 by use of a spot welder 12, and the assembly is finished.