To prevent a component from being separated from a counterpart component inadvertently if an object collides with the component.

An engagement piece 6 is provided on right and left outside ends 4a of a finisher 4 which is the component to be attached. An engagement part 7 to be engaged with the engagement piece 6 is formed on a sidewall part of a case body 2 which is the counterpart component. A pair of leg pieces 6b having a forked shape is formed on an insertion end part 6a to the engagement part 7 in the engagement piece 6. Attachment protruding parts 6c erected with a clearance are formed on each of the leg piece parts 6b. A fitting protrusion part 7c fitted between the attachment protruding parts 6c along the engagement direction to the engagement part 7 of the engagement piece 6 is formed on an insertion rear end 7a into the engagement piece 6 in the engagement part 7. Both of the attachment protruding parts 6c and the fitting protruding part 7c are coupled to each other via a welding caulking part 8 by welding and caulking the individual end parts of both of the attachment protruding parts 6c and the fitted protruding part 7c in the condition of fitting the fitting protruding part 7c between the attachment protruding parts 6c.