To precisely recognize a bar code in an image with a low resolution photographed by a small-size image sensor built in a portable terminal.

After binarization, from a labeled input image, an adjacency relation of a connected region is analyzed on the basis of characteristics of a bar code structure, and a bar code area is extracted. From the width of the connected region of a black pixel inside the extracted bar code area, a unit width serving as a module width of the bar code is decided. When a defined bar code pattern and the inputted width pattern are collated with each other according to order of magnification of the unit width, the bar code is recognized. In collation, an allowance range is arranged for each magnification of the width collation, so that influence of noise and the like is reduced.