The manipulability for wire suspension mechanisms is discussed. For kinematics of a wire driving mechanism, we need not only the geometrical constraints of wire lengths but also the force constraints that each wire tension should be always greater than or equal to zero. First, the sufficient and necessary mechanical conditions corresponding to the force conditions are shown. Using these conditions, we can obtain the manipulability of a wire driving mechanism almost same as that of popular multi-link manipulators. Second, a more practical evaluation index including wire tensions that are driving forces for the object is proposed as“manipulating force set”and the way of calculation is shown. We also derive both manipulability indexes of wire suspension mechanisms in gravity field by modeling the gravitational force as a wire with the tension of the gravity. Numerical examples are given to explain the proposed methods and to show their validity. The method is expected to be effective in designing and task planning of wire driving systems including wire suspension mechanisms.