This paper introduces a model based control of a robot with free joints driven by wires. The robot system is a small serial-link robot. It comprises tubes with small diameters and two pairs of wires. The tubes are used as links and the wires, which pass through the other links, are connected to the interior of the terminal link. The system is driven by the electrical motors via the tension in the wires. Then we have to pay attention to the principle that the each joint torque is generated by the tension. To perform it, we have to derive the mathematical model for the system. Furthermore,the mathematical model is evaluated whether the model can be applied well to controller design by comparison between the simulations and the experiments. The control laws used in the simulation and the experiment are designed to regulate the sum of all joint angles.