Fanfiction culure is being wide spread among N generation in Cyberspace. Fanfiction tends to infringe original author or copyright holder s copyright such as right to maintain integrity as a moral right and right to produce derivative works as a property right because it uses the original work without author’s permission. Meanwhile, in certain cases, fanfiction can be regarded as a fair use under the Copyright Act, that is not a violation of a copyright. However, as commercial or obscene uses are increasing, conflicts between original authors and fanfic writers are also increasing. Accordingly, purposes of this paper are to find the legality of fanfiction based on copyright laws and cases, and to suggest guidelines to fanfic creators and copyright holders of original works to settle and flourish subculture of fandom.