PURPOSE: To prevent the damage of a cross member and a reinforcing member effectively by forming a nut of a cast product provided with a base part with a threaded hole to be screwed with a bolt, and a bent part formed in the bent state at one end of the base part so as to come in contact with a plate part adjacent to the fitting flange of the cross member.

CONSTITUTION: A nut 24 is formed of a base part 24a coming in contact with a fitting flange 20, a clamped member, and a bent part 24b formed in the bent state at one end part of the base part 24a. A disc-shaped protruding part 24c is formed at the base part 24a, and the protruding part 24c is provided with a threaded hole 24d bored so as to be screwed with the screw shank part of a bolt 14. Since the nut 24 is a cast product, the cross-sectional shape of a connection part 24c between the base part 24a and the bent part 24b can be easily formed into such optimum shape as to prevent stress concentration based on bending load or at least reducing the degree of stress concentration sufficiently compared to a conventional reinforcing member.