PURPOSE: To not only confirm an inserted document, but also edit it later by displaying the storage contents of an external storage device.

CONSTITUTION: According to whether or not the mode (i.e., attribute information) of a merge position (OB-P-M, refer to Fig. (A)) is set, which of the mode of the merge position and the mode of a merge document is made effective can be selected for a document (refer to Fib C) after merge execution. Namely, attribute information is granted to each character of an 'insert character string' refer to (Fig.B) to be inserted into the document and the attribute of each character included in the 'insert character string' is determined (Fig.C) according to the relation with the attribute information (Cnt) previously granted at the insertion position (OB-P-M) in the document and then stored on the external storage device.