A mounting body 100 in accordance with the invention is mounted to a bolt body from a side portion of the bolt body. The mounting body 100 is provided with a mounting portion 10 having an engagement portion 20 provided with an engagement projection 21 engaging with an outer thread of the bolt body, an opening portion 70 moving forward the bolt body into the engagement portion 20, and adjacent portions 30 arranged in a leading end side of the engagement portion 20. The mounting body 100 can be mounted to the bolt body by moving forward the bolt body from the opening portion 70 of the mounting portion 10, thereafter plastically deforming the engagement portion 20 so as to make the adjacent portions 30 relatively close to each other, arranging the engagement portion 20 along an outer surface of the bolt body, and maintaining a state in which the engagement projection 21 is engaged with the outer thread of the bolt body.