This paper studies the issue of conceptually indexing the blogosphere through the whole hierarchy of Wikipedia entries. This paper proposes how to link Wikipedia entries to blog feeds in the Japanese blogosphere by machine learning, where about 300,000 Wikipedia entries are used for representing a hierarchy of topics. In our experimental evaluation, we achieved over 80% precision in the task. Categories and Subject Descriptors H.3.0 [INFORMATION STORAGE AND RETRIEVAL]: General General Terms Keywords blogosphere, Wikipedia, blog feed retrieval, topics