A beam member is fixed to a side member of a vehicle body. The side member is provided with a nut member and a reinforcing member. A bolt is inserted into the nut member from under the side member. The reinforcing member includes first and second plate portions. The first plate portion includes a pair of flanges that are bent individually at bent portions. The respective positions of the bent portions are adjusted depending on a distance between sidewalls of the side member. The flanges are welded to the sidewalls. The second plate portion includes a base portion welded to the lower end of the nut member and an upright portion extending along the nut member.