PURPOSE: To eliminate necessity for spreading a link each time a document is prepared by inputting, storing a relation between the documents and referring the relation when the routine document is prepared.

CONSTITUTION: A format editor 31 is provided to execute the preparation and edition of a format net, and an editor 32 is provided to execute the preparation and edition of the routine document. Then, a format library 33 is provided to store format net and a document storage 34 is provided to store the document prepared by the editor 32. The format of the document or the relation between the documents are registered and inputted in advance for each document system and when the routine document is edited, the document is automatically made relative while referring the registered format or the relation. The format of the routine document or the relation between the documents is defined and stored independently of the editor to prepare the document. Thus, it is not necessary to spread the link each time the document is prepared, and the format of the routine document of the relation between the documents can be easily changed.