The Japanese public attitudes toward nuclear power generation had become negative year by year. After the Chernobyl accident, a percentage of the unfavorable respondent toward nuclear power generation has dramatically increased, and a new type of anti-nuclear movement has been observed. On the basis of our public opinion polls, the reason for this increase was found to be primarily decrease of sense of usefulness rather than increase of sense of uneasiness about nuclear safety. Particularly, social factors (change of life style, progress of civilian consciousness, credibility of the existing institutional system etc.) have influence on the attitude of either pro or anti-nuclear. Based on the above observation, we have inferred that process of the public attitudes has two flows arising from the above social factors, one is the usefulness and the other is the easiness about nuclear safety, and have formulated a model representing the process of public attitudes toward nuclear power.