The nuclear power plant disaster in Fukushima Prefecture has given big influence on our life. Such influence is due to not only the accident itself but many things resulting from the rumor which the accident brought about. This paper, first of all, points out several problems we have to cope with. One of the most serious one is that because the Tokyo Electric Power, the government, and the mass media do not understand the difference between data and information and because they do not recognize the importance of information, they provide unsuitable data to disaster victims and average citizens in many cases. In addition, the fact that disaster victims and average citizens considerably lack the knowledge about the accident and its effects can not be ignored. As the result, they become uneasiness and are prone to act improperly. Secondly, it describes the situation of the disaster from the mutual relation among phenomena, data, information, and knowledge. Finally, three ways of coping, by which disaster victims and average citizens can act appropriately and avoid damages caused by rumors, are proposed as follows. a) The Tokyo Electric Power, the government, and mass media must try to raise information consciousness and sense markedly. b) Disaster victims and average citizens must examine carefully the data provided from them before making any decision. c) An organization of the national level should be established immediately, in which specialists will lecture disaster victims and average citizens on the fundamental knowledge about the accident and its effects.