An information retrieval system comprises a storage section that stores location information about information selected by a user as a document location information database, an analyzer section that analyzes frequency of utilization of each location information in the document location information database, a retrieval information accumulating section that accumulates information in a predetermined accumulation range on an accumulation base point corresponding to location information having the frequency of utilization equal to or more than a threshold value, as a retrieval information database, and a retrieval section that retrieves required information from a retrieval information database based on a retrieval condition designated by the user.