Abstract: Provided is a data management method. Data corresponds to an entry including a reference to another entry and is managed in a set which is a collection of pieces of the data. The set corresponds to a linked list where the entry corresponding to the data is linked in order of addition of the data. The entry includes an insertion time sequence number inserted into the linked list and information indicating if the data has been deleted from the set. In that case, the entry is separated from the linked list at a predetermined timing. The linked list is traced to refer to the data. When the insertion time sequence number of the reference entry is later than the insertion time sequence number of the entry which has already been referred to, it is judged that the reference entry has been separated from the linked list.