The gas absorption spectroscopic measurement device according to one embodiment of the present invention is provided with: a laser irradiation unit (1); and optical resonator (2), and a first detection unit (3) for detecting light taken out of the optical resonator (2). The gas absorption spectroscopic measurement device acquires the component concentration of a gas to be measured by CRDS (Cavity Ring-Down Spectroscopy) measurement. The laser irradiation unit (1) is provided with: a laser light source (10); a frequency conversion unit (12) configured to selectively output either laser light having the same frequency as the irradiation light source or laser light having a frequency of the laser light source multiplied by a prescribed number of times; a frequency modulation unit (13, 14) for modulating the frequency of the emitted laser light using a modulation signal, a second detection unit for detecting returning light derived from the irradiation light returning to the optical resonator (2); and a feedback control unit (191, 11) for generating an error signal affected by the difference between the frequency of the laser light emitted to the optical resonator (2) and the modulation signal based on the detection signal from the second detector (18), thereby controlling the oscillation frequency in the laser light source (10) in accordance with the error signal.