To fasten an item to be fastened, which is one out of the plural kinds of radial dimensions, with one kind of a fastening device by specifying each interference, and each fastening form.

This fastening device is formed out of an annular portion 10b having a cut-out opening 10a, paired projected pieces 10c extended outwardly from both the end parts of the opening 10a, six holding bodies 16 which are integrally formed at the upper end parts and at both the end parts of the paired projected pieces 10c respectively while being different in thickness, and of a bolt 12a and a nut 12b. In this case, one holding body 16 having thickness corresponding to the diameter of an item to be fastened, is selected so as to be held in between the paired projected pieces 10c, so that the paired projected pieces 10c and the holding body 16 are thereby fastened with the bolt and nut 12a and 12b.