LOWER PART VEHICLE BODY STRUCTURE OF MOTOR VEHICLE

To secure rigidity of a frame member against a load applied from a rear wheel.SOLUTION: In a lower part vehicle body structure of a motor vehicle, at a vehicle fore and aft position which corresponds to a front side end part of a trailing arm 21 in a frame member (a support frame 100), a gusset 60 is provided having: a gusset front side wall part 61 joined to an outer side wall part (a support frame outer side wall part 103) as seen in a vehicle width direction and a lower wall part (a support frame lower wall part 102) of the frame member; a gusset rear side wall part 62 which is provided spaced apart from the gusset front side wall part 61 to the vehicle rear side and joined to the outer side wall part as seen in the vehicle width direction and the lower wall part of the frame member; and a gusset side wall part 63 connecting an inner end part of the gusset front side wall part 61 as seen in the vehicle width direction and an inner end part of the gusset rear side wall part 62 as seen in the vehicle width direction.SELECTED DRAWING: Figure 3 【課題】後輪からの荷重に対するフレーム部材の剛性を確保する。【解決手段】フレーム部材（支持フレーム１００）内におけるトレーリングアーム２１の前側端部に対応する車両前後位置に、上記フレーム部材の車幅方向外側の側壁部（支持フレーム外側側壁部１０３）及び下壁部（支持フレーム下壁部１０２）にそれぞれ接合されたガセット前側壁部６１と、該ガセット前側壁部６１に対して車両後側に離間して設けられかつ上記フレーム部材の車幅方向外側の側壁部及び下壁部にそれぞれ接合されたガセット後側壁部６２と、ガセット前側壁部６１の車幅方向内側の端部とガセット後側壁部６２の車幅方向内側の端部とを連結するガセット側壁部６３とを有するガセット６０を設ける。【選択図】図３