PURPOSE: To enable reading at high resolution by condensing an optical signal reflected by means of irradiation to a bar code, spectrally splitting the optical signal, detecting the specified optical signal and reading it.

CONSTITUTION: An optical beam oscillated by a laser diode 1 which oscillates a coherent laser beam is diffracted and scanned on the bar code 5 by a hologram 3. The optical signal of an image obtained by condensing the reflected optical signal by the hologram 3 is spectrally splitted to a light detector 6 by the transparent type hologram 2 (or a reflection type hologram 2-1), the specified optical signal is detected and the bar code is read. Therefore, an apparent beam diameter by the oscillation wave length change of the laser diode 1 does not become thick so that the bar code 5 is always detected and read at high resolution.