A system allows related documents to be retrieved using conventional search engines while overcoming the ambiguity of a search key entered by the user. The system includes a word sense associative network display portion for displaying word senses of the search key entered by the user together with related word senses in a network, a search portion for conducting a search by generating a search key based on word senses selected by the user, and a filtering portion for selecting documents from the result of the search that matches the selected word sense.