With respect to retrieving documents of interest using a search system, it is made possible to provide a document search system for retrieving documents of interest efficiently and intuitively. Along with a display of a list of search results, new query candidates as well as the hit counts returned with those queries are presented. Specifically, there is provided: a related word dictionary in which related words of search keywords are gathered; a related word query generation processing part configured to extract from the related word dictionary a related word of a search keyword contained in a first query that has been entered, and to generate a second query, which is a new query, using the related word; a search execution part configured to calculate an increase/decrease between the hit count for search results returned with the first query and the hit count for search results returned with the second query; and a search result display processing part configured to simultaneously display on a display part: the first query; the search results returned with the first query; the hit count for the search results; the second query; the hit count for the search results returned with the second query; and the increase/decrease.