The authors have proposed that one of the sources of self-loosening is due to the relative slips which are occurred by the radial deformations between the engaged screw threads and between the contact surfaces at the bearing surfaces of bolt and clamped parts when an external loading is applied to a bolted joint. In this study, the radial deformations of bolted joints fastened by a hexagon nut with flange and by a skirt nut with flange are calculated by Finite-element method. Using the calculated radial deformations, the self-loosening characteristics of the bolted joints are discussed. As the result, it is clarified that the self-loosening is not tended to be occurred in the bolted joint fastened with a nut of which the radial deformation is smaller.