A technique to maintain the fast search capability for the large-scale documents without causing the update delay is provided. This search processing method includes: causing an index search unit for carrying out an index search using a search index before document update to carry out the index search relating to a search request, and obtaining a first list of document IDs of pertinent documents; causing a string pattern matching unit having document contents after the document update to carry out a string pattern matching relating to the search request for the document contents after the document update, and obtaining a second list of document IDs of pertinent documents; and generating a search result for the search request by using the first and second lists and a third list of document IDs of documents relating to the document update.