PURPOSE: To prevent double read-in of the same document, by describing the characters or symbols which can be judged as illegible on the character recognition at a specified location on the document, at the read-in of document.

CONSTITUTION: The sensor 11 picks up the characters and symbols of the area 21 of the document 2, the recognizing section 12 discriminates the characters, and the output is transferred to electronic computers with the output unit 14 via the control section 13. After all the data in the document 2 are read in, the marker drive circuit 16 is operated with the instruction from the control section 13 to describe the mark more than a given size on the area 22 of the document 2. In this case, the size of the mark described in the area 22 is set more than the size which is discriminated outside of the recognition by the character reader, and the control section 13 controls that the data of document of this discrimination is not transferred to the output unit 14. Thus, even if the same document is again read in, no data is transferred in this case to prevent double read-in.