PURPOSE: To enable an exterior panel to be properly and safely fitted to a mounting tool, even when the size, shape or the like of the tool is roughly set, by keeping the bulge section of the panel coupled to the tool, and caulking the recess section of the panel to the neck lower section of the engagement section of the tool, using a coupling tool.

CONSTITUTION: The bulge section 3B of an exterior panel 1 is lightly coupled to the engagement section 2B of a mounting tool 2, and the recess section 3C of the panel 1 is caulked to the neck lower section of the engagement section 2B of the tool, using the recess processing section 14A of a coupling tool 10. As a result, the exterior panel 1 can be properly and safety fitted to the mounting tool 2, even when the size, shape or the like of the panel 1 and the mounting tool 2 is roughly set.