At the docking of a three-dimensional moving vehicle to a fixed base in deep water, an automatic system is indispensable to assure reliable and safe operation, and authors proposed an automatic docking system using ropes for such situation. In the first report, the investigation was focused on the practical feasibility of real time state estimation which is the most significant at the docking, and it is shown that a near optimum filter can be effectively utilized to estimate the state variables of the moving vehicle, based on which the vehicle can be controlled by the ropes. In the first report, proportional control law was applied to check controllability of the system by the ropes, although it is not sufficient for the docking which requires accurate access to the docking point along the desirable trajectory avoiding collision or unexpected oscillations. Therefore, an optimal control technique is introduced to improve control performance of the system, and practical feasibility, especially that of real time computation is investigated. Considering the system requirements and computational feasibility, the system equations are linearized and linear regulator algorithm is applied for the docking control. The system performance is investigated by simulation study, and the following results are obtained. 1) Proposed control algorithm based on the optimal regulator can control the system fast and stably compared with the proportional control law by selecting adequate control parameters through the simulation study. 2) It is shown that real time control by conventional mini-computers is possible if only there are enough memory capacity for storing feedback control coefficients computed in advance. The off-line optimizing computation is not so difficult for this problem formulation, and it can be also computed by a small computer. 3) The system can control the vehicle stably when it approaches within ±5×5 m area in horizontal plane and 10 m above the base. This is easily realized by conventional control system using ultrasonic positioning systems. 4) When the vehicle is controlled based on the filter outputs, i. e., estimated state variables, overall control accuracy of the system is the same order as the filtering accuracy, which is sufficient for the docking requirements.