PURPOSE: To widen the readable range of an object by measuring a distance between a detection object and a bar-code scanner, and changing an image forming position of a laser.

CONSTITUTION: By a distance measuring means 111 of a bar-code scanner, a distance to a detection object for moving relatively in the single direction is measured by a time difference between a radiation time of energy radiated to the object and an arrival time of its reflected energy. Also, a laser light is outputted by a laser light output means 113, and in an optical system 115, an image forming position of the laser light is varied in accordance with a distance to the detection object detected by the distance measuring means 111. Subsequently, the laser light reflected by a bar-code which is put to the detection object is photodetected by a discriminating means 117, and read data of the bar-code is transferred to a host computer. Next, a distance between the detection object and the bar-code scanner is measured, and by changing an image forming position of a laser, the readable range of the detection object is widened.