In the previous report, we investigated the optimal fingertip force for 3-fingered robot hands in two-dimensional space. Generally robots manipulate objects in three-dimensional space. In this report, we consider three-dimensional space manipulation. As with the two-dimensional case. the problem is reduced to a linear programming problem, where the optimal solution is obtained via three-stage optimization solvable by the simplex method. However, in this paper a new criterion is introduced, which leads to a more desirable solution.