PURPOSE: To protect an appearance in the designated range of a document from the destruction of the appearance due to the change of a format or the document so as not to be changed in the designated range.

CONSTITUTION: An operator inputs the start point and end point of the range to be protected to the document inputted by an input means 11 or the document stored in a document storing means 15 by using the input means 11, and a control means 14 dispatches the range having the start point and the end point to a protecting range processing means 16 and instructs the inverted display of the designated range to a display means 12. When the operator erroneously instructs correction or the change of the format in the protecting range to the input means 11 in the state of designating the protecting range, the change is instructed to the control means 14 by the protecting range processing means 16, and the change in the protecting range is disabled.