A suspension system structure is provided which permits a suspension arm to be disposed without being affected by a driven sprocket or a brake disc. A final drive case is supported on rear portions of left and right vehicle body subframes. A driven sprocket and a brake disc are coaxially disposed on the left and right of the final drive case. The driven sprocket and the brake disc are disposed on the inside of the vehicle body frame. An upper arm and a lower arm are disposed on the outside of the vehicle body frame. Support portions of the upper arm and the lower arm relative to the vehicle body frame are overlapped partly with the driven sprocket and the brake disc in a side view to provide a guard therefor.