PURPOSE: To dispense with displaying the content of each document file and to facilitate the operation of an operator by attaining the display of the construction of a document consisting of plural files on a display means.

CONSTITUTION: CPU 12 reads a prepared document and its management information table from a document memory 15 and writes them in a floppy disk through a floppy disk device. Then, after retrieving a document corresponding to the indicated document file name on the floppy disk, CPU 12 reads tree information from management information and displays it on a display screen 19. The operator specifies an item file desired to prepare by positioning a cursor at an item name on the display screen 19. CPU 12 calls file information of the item name specified from the floppy disk to the document memory 15 by the specification. CPU 12 displays file information in the document memory 15 on the display screen 19 and prepares the document on the document memory 15 in accordance with the inputted instruction of a document processing.