In the current global information infrastructure of computer and network, the distribution of information is without boundaries, and the application of information has become complicated and with more varieties. It is very important that we have the correct copyright concept to avoid any infringement while using the copyrighted work. At present, in our country, there is no reference of legal precedents for fair use of copyrighted work. In this paper, the fair use doctrine including the purpose and character of the copyrighted work used, the nature of the copyrighted work, the amount and substantiality of the portion used, and the effect of the use upon the value of the copyrighted work, is illustrated with legal precedents in the United States.Since copyright is entitled from the benefit of the copyrighted work used, the extent of fair use by economic analysis is tried to be explained.