A rear end of a torsion bar is fixed to a distal portion of a spring plate so that the rear end of the torsion bar is in a position other than front to rear direction of a cross member. Thus, when a load is applied to the suspension system in the front to rear direction, the spring plate elastically deforms in this direction. Therefore, the suspension system can prevent the torsion bar from directly contacting the cross member. Also, the suspension arm has two arm portions each of which is supported by two pivot portions. The body has sufficient rigidity against a load applied in the lateral direction thereof. When a load is applied in the front to rear direction, the spring plate elastically deforms, thereby moving the suspension system in this direction. When a load is applied in the vertical direction of the body, the torsion bar twists. With this reaction force, a suspension force takes place and the spring plate bends. Thus, an excessive bending force is not applied to the torsion bar.