Abstract: A suspension arm whose required strength is relatively small and which improves efficiency of space utilization. The arm body of the lower arm of a front suspension has a C-shaped cross section which is open toward the bottom. The top face of the arm body is positioned under a load acting plane. The shear center of cross section of the arm body can be positioned substantially in the vicinity of the load acting plane. A torsion caused by an input load is reduced, so that the arm body has an excellent torsional rigidity. Since the load acting plane is located outside the arm body, a space provided outside the arm body can be increased accordingly. Further, since a required strength of the lower arm can be made smaller, the cross sectional area of the lower arm can be decreased. This decreases the distance between the closed end and the open end of the arm body, thereby providing a sufficiently large space outside the arm body with a resultant improved efficiency of space utilization.