PURPOSE: To make plural alterations at the same time while maintaining the consistency of information for a file to be edited, and to maintain the consistency of information between the object file to be edited and a relative partial area not to be edited at the time of editing operation.

CONSTITUTION: One editing device 4a when starting editing the partial area 2a of a 1st file to be edited inquires the possibility of editing of one exclusive control table controller 5a. The exclusive control table controller 5a checks whether or not the editing operation can be done by referring to an exclusive control table 8 and updates the exclusive control table 8 when the editing operation can be performed so as to indicate that exclusive control is carried out. Then the relative partial area of the partial area 2a of the 1st file to be edited is checked by referring to a relative information table and when the area is found, the exclusive control table 8 is updated by regarding it as an object of the exclusive control. Then the editing operation is performed and at its end, the exclusive control table 8 is put back to its original state and the exclusive control is reset.