This paper deals with the problem of force manipulation dexterity of finger mechanisms. First, the ellipsoid of tendon forces is defined, and based on this definition the configuration dexterity of force manipulation of finger mechanisms and the effect, which is caused by tendon transmissions, on configuration dexterity are analyzed. Secondly, in terms of the mapping relationship between the tendon force space and the fingertip mnaipulating force space, the geometric method to establish the sets of manipulating force vector of fingertip at any configuration of the finger is proposed. The sets can describe the force manipulation characteristics of finger mechanisms when the limits of tendon forces are considered. In order to evaluate the real force manipulating dexterity of the fingertip, two new quality measures are also presented. Finally, analytical examples of dexterity of the force manipulation of finger mechanisms are given.