As a steady new network communication tool, Social Media has reached global propertion. This phenomenon gave impacts on societies of all over the world. Above all, people provide information to Twitter and Facebook on a daily basis. So that, vast amounts of data exist on Twitter and Facebook. We expect to gather useful information from Twitter and Facebook. Twitter was changed by The 2011 off the Pacific coast of Tohoku Earthquake. And Twitter greatly contributed to diffusion of information. For example, many users checked the safty of their friends or family. However a lot of false rumor were diffused probably because the source of information is unclear. For disasters which will occur, we must analyze diffusion of information on social media as soon as possible. In this paper, we analyze “How the diffusion of information on Twitter has been influenced by structural change of the network which is made by communication among users. ” As the result, just after The 2011 off the Pacific coast of Tohoku Earthquake the network has become easier to diffuse various information. However this means that misinformation are diffused too. We also found that a few users believed misinformation without being corrected.