Gravity balancing is often used in industrial machines to decrease the required actuator efforts during motion. In this paper, we present a new design for gravity balancing of the human leg using an external orthosis. This external orthosis is connected to the human leg on the shank and its other end is fixed to a walking frame. The major issues addressed in this paper are as follows: (i) design for gravity balancing of the human leg and the orthosis, (ii) kinematic compatibility of the human leg and the external orthosis during walking, and (iii) comparison of the joint torque trajectories of the human leg with and without external orthosis. We illustrate feasible 2D and 3D designs of the external orthosis through computer simulations. Our results show that the 3D design has smaller inertia with respect to 2D design, which can be more helpful for typical stroke patients to walk in a balanced position.