1. An information processing apparatus for creating a retrieval result displaying a list of retrieval documents, comprising: a document retrieval part configured to retrieve the retrieval documents corresponding to a retrieval condition by conducting a full text retrieval of documents; a document scoring part configured to order the retrieval documents by scores indicating degrees of relevance to the retrieval condition; a feature word file database configured to register a document identification identifying a document, feature words extracted from full text data of the document, and weight values indicating weights of the feature words in which the feature words and the weight values are corresponded to the document identification, for each of the documents; and a document clustering part configured to conduct a clustering process with respect to the retrieval documents based on the feature words and the weight values of the feature words acquired from the feature word file database, by using the document identifications of the retrieval documents as keys, wherein said information processing apparatus further comprises a document grouping part configured to group the retrieval documents based on the scores, wherein the document clustering part conducts the clustering process with respect to the retrieval documents in a group, for each of groups to which the retrieval documents are grouped by the document grouping part.