A new structure of joints in surgical tools is proposed in this paper. Using this new structure, it becomes possible to operate a surgical tool with multiple degrees of freedom and smooth motion. In this new structure, a middle plate connects two parts that have rolling contact between each other. Furthermore, some drive wires are wired so that they cross between the two parts. There are two main features in this new structure. First, the path length of the wires is independent of the joint angle. Secondly, the joint and grippers are controlled independently. Using the independence of the grippers from the joint the operation of the surgical tool becomes easier for the operator. This is because it becomes possible to control the joint and grippers like the wrist and hand of a human being.
