PURPOSE: To eliminate a need of the operation to display the position before the display magnification change after this change by displaying a selected editing base point position and a display base point position one over the other.

CONSTITUTION: Processing procedures are stored in a ROM 7 and are executed by a CPU 6. That is, the size of the display picture for data display is acquired. The size of the picture area which can be displayed (editable area) on a CRT 1 is acquired from an acquired display magnification. The acquired size of the picture and that of the picture area are compared with each other, and the processing is switched in accordance with the result. If the whole of the picture cannot be displayed in this case, the editing base point position is set, and the display base point position is set. Thereafter, the control related to scroll is performed based on acquired sizes. The scroll position of the picture is obtained so that the acquired editing base point position and the acquired display base point position coincide with each other, and the scroll position is set.