This study aims to achieve an optimal design through Multidisciplinary Design Optimization (MDO) to reduce the manipulator’s weight. This approach enables the creation of a more energy- and resource-efficient manipulator. Previous research has focused on reducing the weight of manipulators by optimizing individual components. In contrast, this study takes a comprehensive approach, optimizing the entire manipulator as a whole. Earlier work of this study considered geometric and dynamic disciplines in MDO and optimized various parameters, including the manipulator’s installation position, motor and reducer configurations, and link lengths. Additionally, we proposed the Directional Manipulability Index (DMI) to account for manipulability in the path direction. This presentation extends the MDO framework to a 6 DoF manipulator, incorporating DMI into location optimization. The proposed method has been integrated with an optimization algorithm and implemented in practice, resulting in significant weight reductions. Moreover, the motor and reducer weights have been minimized compared to conventional designs, leading to a more energy-efficient manipulator.