A data retrieval method in a data-string set including a plurality of data strings, each data string having a data identification name storage area, a parent data storage area storing link-information data, wherein when data strings are consecutively traced on the basis of link-information data stored in parent data storage areas of data strings, with arbitrary link-information data stored in the parent data storage area of a certain data string as a starting point, until the parent data storage area of the traced data string is empty, the link-information data about the certain data string is included in none of the parent data storage areas of the traced data strings; the method comprising recursively extracting a data string on the basis of link-information data stored in a parent data storage areas of the data string storing a data identification name to be retrieved and the extracted data string, until the parent data storage area of the extracted data string is empty.