With the problem of recent global warming, nuclear power becomes more important energy source in the world. In Japan, however, it is difficult to build new nuclear facilities. One of the reasons is the problem of risk communication. In this study, therefore, a support method has been proposed to improve mutual understanding in risk communication. Especially the authors pay attention to the learning effect of debate and employ a debate support system. A laboratory experiment was conducted to evaluate the proposed method, where 30 university students joined as subjects. As the result, it was found that use of the system could improve mutual understanding especially about reduction measure of the risk and accident management. In addition, debating in the opposite position with the system could improve subjective mutual understanding, however, it is not effective for objective mutual understanding.