To provide a structure and a method of fastening a screw that can prevent a nut from coming off without using caulking in a different method than before.

A structure of fastening a screw includes: a first member 22 having a male screw 22b; a through-hole penetrating the male screw 22b; a second member 120 in which a back facing hole 121b is formed on an opening side of the through-hole; a female screw 174 fastened by the male screw 22b; and a nut 170 having an exposed thread outer peripheral surface 172 fastened with an exposed thread with respect to the inner peripheral surface of the back facing hole 121b.