This paper discusses the mechanics of coordinative manipulation by multiple robot manipulators or a multifingered robot hand. The coordinative manipulation problem is divided into two phases. One is determining the resultant force by multiple robotic mechanisms, and the other is determining the internal force between them. The resultant force is used for the manipulation of an object subjected by the external forces or the environmental constraints. The internal force is used for adapting the robotic mechanisms to uncertainty and variety of the static friction. A dynamic coordinative control scheme is proposed for determining the resultant forces. The optimal internal force is defined as the internal force that yields the minimal norm force satisfying static frictional constraints. The optimal internal force promotes the stability of prehension, while the conventional method sometimes result in too much internal force and reduce the stability. Finally, by applying a non-linear programming method, it is clarified that the optimal solution is necessarily obtained by solving, at most, 2(2^m-1) (m is the number of robotic mechanisms) sets of algebraic equations if it exists.