A laser device for an analyzer, comprising: a laser light source that outputs light having a center wavelength near an absorption wavelength of an analysis object, a wavelength selection element that receives a part of the light output from the laser light source and that selects and leads out the light having a wavelength substantially equal to the absorption wavelength of the analysis object from among wavelengths of the light output by the laser light source, a light detection device that detects intensity of the light led out from the wavelength selection element at the selected wavelength, a single substrate that is equipped with the laser light source, the wavelength selection element and the light detection device whereby the wavelength selection element is configured to select a wavelength in dependence on the temperature of the substrate; a control device configured to control the temperature of the substrate to a constant level corresponding to an absorption wavelength of the analysis object, and a temperature adjusting device that is mounted to the back surface of the single substrate and that, under control of control device, adjusts the temperature of the single substrate to a constant level which determines the wavelength selected by the wavelength selection element, wherein the temperature adjusting device is configured to control the temperature of the single substrate so as to match the wavelength of light led out from the wavelength selection element to be substantially equal to the absorption wavelength of the analysis object from among wavelengths of the light and the control device configured to increase or decrease a drive electric current of the laser light source near a specified electric current value so as to cause the laser light source to output light of the above-mentioned absorption wavelength by setting the drive electric current at an electric current value at which the intensity of the light detected by the light detection device after selection by the wavelength selection element becomes a peak. a laser light source that outputs light having a center wavelength near an absorption wavelength of an analysis object, a wavelength selection element that receives a part of the light output from the laser light source and that selects and leads out the light having a wavelength substantially equal to the absorption wavelength of the analysis object from among wavelengths of the light output by the laser light source, a light detection device that detects intensity of the light led out from the wavelength selection element at the selected wavelength, a single substrate that is equipped with the laser light source, the wavelength selection element and the light detection device whereby the wavelength selection element is configured to select a wavelength in dependence on the temperature of the substrate; a control device configured to control the temperature of the substrate to a constant level corresponding to an absorption wavelength of the analysis object, and a temperature adjusting device that is mounted to the back surface of the single substrate and that, under control of control device, adjusts the temperature of the single substrate to a constant level which determines the wavelength selected by the wavelength selection element, wherein the temperature adjusting device is configured to control the temperature of the single substrate so as to match the wavelength of light led out from the wavelength selection element to be substantially equal to the absorption wavelength of the analysis object from among wavelengths of the light and the control device configured to increase or decrease a drive electric current of the laser light source near a specified electric current value so as to cause the laser light source to output light of the above-mentioned absorption wavelength by setting the drive electric current at an electric current value at which the intensity of the light detected by the light detection device after selection by the wavelength selection element becomes a peak.