PURPOSE: To easily execute the alteration work of document title information.

CONSTITUTION: A control part 1 obtains a title system alteration indication and the content from an input part 2. A title system/document title information alteration circuit part 8 converts the information and a title system obtained from a title system/title display form recording part 3 into a new title system and a title display form, records them again, generates document title information alteration data by the altered title system obtained from the title system/ title display form recording part 3 and by the alteration method of document title information from the input part 2 and stores it in a document title information alteration data storage part 7. The title system/document title information alteration part 8 converts document title information on an existed document into new one and records it again based on document title information alteration data obtained from the document title information alteration data storage part 7.