A mobile terminal reads a read manuscript as image data. A character recognition block performs character recognition from the image data, which is read, on the basis of a threshold for judgement of unrecognizableness. A character recognition result is transmitted to a central control unit, or the threshold for judgement of unrecognizableness is received from the central control unit in a threshold receiver. On the other hand, the central control unit receives the result of character recognition from the mobile terminal, or transmits the threshold for judgement of unrecognizableness from a threshold transmitter to the mobile terminal. Furthermore, the central control unit controls the threshold for judgement of unrecognizableness with a threshold controller.