Fastening structure

A fastening device for fastening an attaching member to an attached member, the fastening device comprising:

• a bolt having a head portion and a threaded portion integrally formed with the head portion, a bottomed tubular bolt cover integrated with the bolt and having an opening end, and a cap member accommodated in the bolt cover, closing the opening end of the bolt cover and having a first engagement portion formed thereon,
• the bolt cover has a through bore configured to have the threaded portion of the bolt pass through, a bottom portion abutting on a bottom surface of the head portion of the bolt, and a grip portion projecting from an outer circumference of the bottom portion, surrounding a periphery of the head portion of the bolt, and having a second engagement portion configured to engage with the first engagement portion and formed on an inner peripheral portion thereof,
• the second engagement portion is constituted by a protrusion inwardly projecting from the inner peripheral portion of the grip portion of the bolt cover, the bolt is constituted by a washer bolt provided with a small diameter portion formed on an upper end of the threaded portion thereof and a washer received and retained on the small diameter portion,
• a distance between an outer diameter of the washer and the inner peripheral portion of the grip portion is smaller than a distance between an inner distal end of the protrusion and the inner peripheral portion of the grip portion, such that the washer is made to catch the second engagement portion as the bolt is moved towards the opening end of the bolt cover, and
• the bottom portion of the bolt cover is interposed between the bottom surface of the head portion of the bolt and the attaching member in a state that the attaching member is fastened to the attached member via the fastening device.