A keyword search method is provided to show a web document highly related to keywords that a user sincerely wants. A set recommendation keyword set correspondingly to a search keyword that a user inputs is read(S206). A web document including the search keyword is searched(S207). The web document including the recommendation keyword is searched(S209). A ranking list is generated by scoring web documents including the search keyword(S211). According to the ranking list, summary information of each web document including the search keyword is generated(S213). The summary information is provided to the user(S214).
