PURPOSE: To prepare a document using correct sentence expression by informing the contents of processing to a document composer when the editing processing of a certain part in a document exerts influence upon another part in the document in the document editing processing.
CONSTITUTION: While displaying all or a part of a document in preparing by a display means 7, the contents of a document to be formed or a command for editing the document is inputted by a document input means 6. The document is prepared and stored in a document storing means 3. An editing processing means 2 executes editing processing corresponding to the characters or the command inputted from the means 6. At the time of inputting a command for editing processing, whether the editing processing applied to a part of the document by the command exerts influence upon another part of the document or not is decided by a reference relation deciding means 5. When the editing processing exerts influence, the contents are informed to the document composer.