1. A file search system for searching for a file stored in a storage device, comprising: reception means for receiving a search request made by a user; search means for obtaining search result files by searching the storage device on the basis of notification from the reception means; monitor means for monitoring a file operation by the user; creation means for creating a reference relation of the file on the basis of a monitor result of the monitor means; storage means for storing the reference relation; importance calculation means for calculating an importance of the file on the basis of the reference relation; and search result sort means for arranging the search result files obtained by the search means on the basis of the importance.