An existing study in cognitive psychology found a phenomenon that humans recall less on contents uttered in a condition where there is an inconsistency between contents and ways of utterances on positivity and negativity. The aim of the research is to explore whether the similar phenomenon causes in Human-Robot Interaction. A psychological experiment ( N =45) was conducted with 2 × 2 between-subject design of polite/impolite phrase of utterance from and postures of a small-sized humanoid robot. The results found that recall task scores of subjects for contents uttered by the robot and their evaluation scores of impression toward the robot were less in the conditions with inconsistency between the robot's phrase and posture on its politeness. The paper discusses some implications of the phenomena from the design perspective of interaction between robots and humans.