To solve the problem that, if a conventional component mount structure is adopted in which a car body and a boss provided integrally in a resin component are fastened by using a screw inserted into a mount hole provided on the car body, stress is concentrated to a coupling portion between the boss and the resin component by adding a revolving load of the screw to the boss in mounting the resin component, a surface of the resin component may be distorted or whitened and appearance quality is damaged.

A resin component mount structure is characterized mainly by comprising a rib 3a. The rib 3a is provided on a cap seat surface 3e that is a surface confronted to a rear-side surface of a rear fender 5 of a cap 3 and inserted through a mount hole 5a. When fastening a screw 4, the rib 3a interferes with an edge of the mount hole 5a.