This contribution aims at introducing an optimal design methodology for the Stewart Platform robot that considers structure and control design variables simultaneously. This methodology intends to maximize the positioning accuracy in order to optimize the overall performance of the robot for a specific task. The structure design variables of the mechanism combined with the gains of the controller are the structure-control design variables, this global set is considered simultaneously in the optimal design methodology. A position control scheme, based on a PD controller, and the complete dynamics of the robot are considered to compute the overall tracking position as function of the structure-control design variables. A sensitivity analysis is performed to evaluate the effect of the structure-control design variables on the tracking position accuracy of the robot. The associated optimization problem is solved by using metaheuristic optimization methods. Simulation results demonstrate that the proposed design procedure is effective to increase the positioning accuracy, as well as to improve the closed loop dynamics performance of the robot.