FASTENING STRUCTURE

PROBLEM TO BE SOLVED: To provide a fastening structure capable of securing sufficient strength while suppressing the increase of the number of parts and the reduction of the degree of freedom of arrangement.SOLUTION: A hollow member 11, made of aluminum and aluminum alloy, is formed in a cylindrical shape having a lid wall part 11c and a bottom wall part 11d facing each other. In the lid wall part 11c and the bottom wall part 11d, a fitting hole 16 and a mounting hole 17 are formed respectively. A steel fastening member 13 is inserted into the fitting hole 16 and contacts the inner wall surface of the bottom wall part 11d at the peripheral edge part of the mounting hole 17. In the fastening member 13, internal threads 22a are formed by drilling from the top end surface that contacts the inner wall surface of the bottom wall part 11d. A bolt 31 is inserted into the mounting hole 17 and screwed to the internal threads 22a. In the fastening member 13, internal threads 24a are exposed from the lid wall part 11c and screwed to the bolt 32 for fastening a fastened member 14.