PURPOSE: To arrange the documents with high efficiency by integrating the pointed plural documents into a single document to store it just with the permutation and the change of the index information contained in an index part without moving the images stored in an image area at reception of an instruction for integration of plural documents into a single one.

CONSTITUTION: In a filing system the pointed plural documents are integrated into a single document and stored just with the permutation and the change of the index information stored in the index parts DI and PI without moving the images C11, C12, C21 - C23, C31 and C32 stored in an image area PC at reception of an instruction for integration of plural documents D1 - D3 into a single one. In such a way, plural documents can be quickly and simply integrated into a single document. Thus the documents are arranged for the benefit of retrieval of them.