在電腦與網路結合的資訊地球村中，不僅資訊流通分享無國界分際，資訊應用更是多樣而複雜化。如何合理使用著作，應有正確的著作權觀，以避免發生侵權情事，是很重要的。 在我未有充分著作侵權判例可供著作合理使用酌參之前，本文以美國判例對著作利用目的與性質、著作性質、著作利用之質與量及利用結果對著作價值之影響四項合理使通則的解釋，以闡釋著作權的合理使用範圍。尤其著作權的主張，主要是基於著作利用的經濟利益，是故，更圖以著作權的法律經濟分析，說明著作的合理使用尺度。

　　　　　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.