In the present paper, a method for extracting user interest by constructing a hierarchy of words from social bookmarking (SBM) tags and emphasizing nouns based on the hierarchical structure (folksonomy) is proposed. Co-occurrence of the SBM tags basically have a semantic relationship. As a result of an experimental evaluation using the user profiles on Twitter, the authors discovered that the SBM tags and their word hierarchy have a rich vocabulary for extracting user interest.