In this paper, we propose a clustering method based on structure of compound nouns. Japanese compound nouns usually provide concrete concepts, thus we can assume that compound nouns must be a good clue to index documents for Web document clustering. The other benefit of using compound nouns is their compositional structure that can be divided into sub concepts. This indicates that we can construct hierarchical Web document clustering based on their structure. From the practical experiments of constructing hierarchical clusters on the results of a Web search engine, we succeeded in showing that the clearly clusterized Web documents with understandable hierarchical indexes of compound nouns.