A bar code having parallel bars carrying information is divided into a plurality of regions so that each region is detected by a field of vision of an image sensor of a bar code reader. The bars in each region are detected by a scanning operation to store data indicative of the width of each bar into a memory. When scanning of a region is completed, detection of another region follows to store data in the same manner. After all the regions are scanned to obtain their data, these data are combined to produce a combined data. Some superfluous data due to overlapping of two consecutive regions are removed from the combined data. In one embodiment, the superfluous data are removed by using data indicative separation bars provided between the two consecutive regions, while in another embodiment, the superfluous data are removed by using a predetermined value indicative of the actual number of bars of the bar code.