This paper studied out the prototype and the structure of UGS(User Generated Storytelling) based on social network in "World Of Warcraf" and "Mabinogi" as MMORPG(Massively multiplayer online role-playing game) and started with issues based on SNS(Social Network Service) in Internet. SNS has been supported by storytelling which is made by users to go through the contents in game space as well as by developers. This study drew elements toward social network in game and its new possibility as storytelling applied by communication theories based on social psychology. Today SNS is a major topic in web environment and this issue has influenced the game design and UGC. Under this situation, this study has a significant meaning because it proves that the factors toward social network in MMORPG is analyzed by UGCs.