Demodulated data B containing the whole of a right block and a part of a left block is obtained after demodulated data A containing a start guard bar (SGB) and based on a division reading process has been at first obtained. When demodulated data C containing an end guard bar (EGB) and numerical data of three characters is thereafter obtained, the demodulated data C is aligned with modulus 10-OK data obtained by synthesizing the demodulated data A with the demodulated data B on the basis of the end guard bar (EGB), and compares the tenth through twelfth characters (of the numerical data) of both of the data with each other. As a result of this comparison, if the tenth through twelfth characters (of the numerical data) of both of the data are coincident with each other, an identical character counter is incremented.