A device divides a table (60) including element information contained in tree-structure information and position information in a corresponding tree-structure into an element information value (61) and position information (62) by a table division unit (101). An element information rearrangement unit (103) rearranges the divided element information values (61) into an order in a dictionary. Correspondence information (703) indicating the order change by this rearrangement is extracted by a correspondence information extraction unit (104). A position information encoding unit (102) and a corresponding information encoding unit (105) encode the position information (62) and the correspondence information (703), respectively. By using the encoded position information (62) and the correspondence information (703) and the element information values (61), a compressed information forming unit (106) forms compressed information from these.