A process for document registration is executed with a structured document of a file as an input. An analyzed structured document and information for document search are generated and stored in databases, respectively. A query input is analyzed, a document search index is read and a search process is executed, producing matching document identifier information and matching strings position information. Then, a corresponding analyzed structured document is read from the database based on the document identifier information, the matching information is embedded in the structured document based on the matching strings position information, and a structured document with added highlight information is generated and displayed. A document is searched from which the element information constituting a stumbling block to the search is removed, and the result of the search is displayed with highlight information added to the original structured document.