To attain highly precise bar code reading prevented from being influenced by the background of a bar code.

A bar code part 10 on a postal matter P is irradiated with excited light radiated from an excited light source 11 and emitted and its optical signal is converted into an electric signal by a line sensor 12. A signal processing part 13 A/D converts an output signal from the line sensor 12 into multi-valued picture data, a bar code area detecting part 14 detects the existence area of the bar code 10 on the postal matter P based upon the picture data obtained from the processing part 13, a ternary run length detecting part 15 calculates the ternary run length feature of the picture data in the bar code area detected by the detecting part 14, and a bar code recognizing part 16 detects bars based upon the thernary run length of the bar code area obtained by the detecting part 15, judges a bar pattern and recognizes the bar code 10.