A transportation system by cooperation of several manipulators has been developed until now. In this report, a practical method of determining grasping points of manipulators is proposed so that the maximum loads for each manipulator shouldn't exceed the payload capacity of the manipulators. First, we propose a searching scheme for grasping points so as not to exceed the load capacity for arbitrary trajectories of position and orientation of the transported object. Then, we verify the effectiveness and efficiency of the scheme by simulations.