A document retrieval system has an index information generator that generates index information about the frequency of occurrence of non-numeric terms in documents, and index information about the numeric values of numeric terms and the types of quantities they represent. Numeric terms received as search conditions are processed by a numeric information generator that generates search information indicating the type and numeric value of each numeric term. The index information generator and numeric information generator preferably convert numeric values to a standard notation. Numeric search conditions can then be used appropriately, flexibly, and conveniently to obtain useful retrieval results.