In this paper, we propose a design methodology of robots based on augmented reality (AR). While robot design based on subjective evaluation is useful, the problem of subject-based design is that the developer should prepare all variation of robots to be evaluated. Using AR, a developer can prepare robots using computer graphics. In addition, the AR technology makes it possible to evaluate a robot in an environment in which the robot is supposed to work. We conducted experiments to evaluate a robot's head size using both AR and real robots, and compared the evaluation results. As a result, similar evaluation results were obtained from both evaluation experiments, which showed a possibility of AR-based robot evaluation.