Abstract : Recently, User Generated Content(UGC) Video on Demand(VoD) services such as YouTube become popular all around the world. In Japan, Nicovideo which is one of UGC VoD service gathers more attention than YouTube. Users in Nicovideo make new contents by adding new features to exisiting contents and categorize contents by using shared tags. These tags cleary represent what the content is. In this paper, we analyze tag co-occurring networks on Nicovideo and extract characters and relations of contents. As a result, it is obserbed that not only category tags but also user defined tags appear as a center of contents. In additon, we can categorize tags using relations between tags.