As the development of electrical transportation systems, two-wheeled mobile robots have been widely studied because of the high mobility. Among them, the two-wheeled wheel chair is the wheel chair without caster wheels, and moves and stabilizes with only two wheels. However, wheel chairs cannot move lateral direction in general, and they sometimes fall down and cause into serious accidents. In this paper, lateral directional mode and its control method are proposed to solve this problem, and the validity of proposal is checked through simulations. The results are evaluated by the movement distance and the change of body's pitch angle.