PURPOSE: To achieve the simplification and speedup of proofreading work by inserting a composing function for starting and finishing the alteration of a format within a desired range of sentence data to indicate a range desired to be corrected, a composing function desired to be corrected and the increase and decrease quantity thereof.

CONSTITUTION: The signal inputted to a control part 2 is given to an input control means 4 and encoded to be transmitted to a proofreading processing means 5. This means 5 reads sentence data consisting of inputted character data and a composing function and the sentence data stored in a sentence data memory part 6 if necessary according to a similarly inputted proofreading command to perform proofreading processing and stores the processing result in the sentence data memory part 6. When the proofreading processing is finished, the indication for operating a composing processing means is sent to the means 7 from an input device 1 through the means 4. The means 7 reads the sentence data processed by the proofreading processing means 5 to apply composing processing to the character data according to the composing function to form composing data. This composing data is delivered to a display control means 8 to be displayed on a display device 3.