1. A document information management system comprising: at least one database or a filing unit for storing therein a plurality of document files comprising a hypertext document previously written with a hypertext-description language such as HTML and/or a non-hypertext document prepared with an application such as word processor; a browser having a browsing function for displaying and operating the hypertext document or the non-hypertext document on a screen; and a search engine having a search-engine function of searching for a corresponding document through the database or the filing unit according to a specified keyword; said browser having a search-engine-compatible interface unit for making a word in a document displayed on the screen to be specified, transferring the specified word to said search engine as a keyword to be used in the search engine, receiving a search result from said search engine, and displaying the search result on the screen; and said search engine having a browser-compatible interface unit for performing a search by using the keyword transferred from said browser and transferring a search result to said browser.