Abstract— In this paper, the robustness of graspless manipulation (or nonprehensile manipulation) is investigated. We derive some new constraints for static frictional forces in graspless manipulation, which gives us more accurate evaluation of the robustness of graspless manipulation than previous studies. We also present a procedure to calculate a measure of the robustness based on linear programming. Numerical examples are shown to prove that our new method works well even when previous methods make an inappropriate evaluation.