PURPOSE: To provide a mold number reading device which can quickly and correctly read the mold numbers, i.e., the binary codes which are arranged in circumference on the bottom of a bottle.

CONSTITUTION: A mold number reading device consists of an image pickup device which photographs the codes and an image processor which decides the codes from the images photographed by the image pickup device and reads the mold numbers, i.e., the binary codes which are arranged in circumference on the bottom of a bottle. The image processor includes a means which sets previously the concentrical circles 12 and 13 to include all code images between both circles, scans the images along these circles, and shifts the center C of the circles 12 and 13 to include all images 11 between both circles and to decide the center and a means which equidistantly divides both circles 12 and 13 into blocks and decides the presence or absence of images in the blocks.