A stop sensing section senses movements by comparing data on two lines separated by a time interval in the same place (line) of the digital image information on the bar codes from a signal processing section and, when there is no movement, outputs a decode start trigger signal to a decoder section. A CPU in the decoder section, receiving the decode start trigger signal, judges that the bar codes have stopped in the proper position, and reads the bar code image information stored in a frame memory at that time for decoding.