PURPOSE: To easily and efficiently perform the editing and correction of a document by parallelly displaying the corresponding logical structure of the new/old document while suitably inserting a space to the new or old document, and synchronously scrolling the display of the new/old document.

CONSTITUTION: This device is composed of an output device 101 such as display, input device 102 such as keyboard or mouse, main body 103 of a computer, project file 104, old document file 105, new document file 106, logical structure corresponding data file 107 and logical structure definition file 108. When the logical structure of the new document is edited or when its size is changed by editing the contents of structure, the corresponding logical structure of the new/old document is parallelly displayed while suitably inserting the space to the new or old document and further, the display of the new/old document is synchronously scrolled. Thus, a worker can easily comprehend and manage the logical structure of the document.