<p>There is disclosed a gas detection device comprising :- a laser which generates a laser beam of a wave length and intensity corresponding to a drive current and the temperature; a laser drive circuit which modulates the drive power source of the laser at a specified amplitude centered around a specified temperature and a specified current value; a means of stabilizing the wavelength by which the central wavelength of the laser beam generated by the laser is stabilized at a specific position on a special gas absorption line; a beam detection apparatus which detects the intensity of the laser beam after the laser beam passes through the measuring object gas atmosphere; and a measuring means which performs a quantitative measurement of a specific gas based on the output of the beam detection apparatus.</p>
