— To explore the design of politeness in embodied conversational agents and social robots from the perspective of user studies, a case study based on a psychological experiment was conducted to straightforwardly investigate effects of polite behaviors by robots in Japan, using a small-sized humanoid robot. Results of the experiment suggested that differences of polite behaviors expressed by the robot affected participants’ impression of and behaviors toward the robot. Keywords- Robots; Politenes; Psychological Experiement