Laser interferometer

Provided is a laser interferometer in which the wavelength of laser light incident on an interference optical system is stabilized. This laser interferometer is characterized by being provided with: an interference optical system which is provided with a laser light source that emits laser light, and which causes the laser light to interfere with each other; a gas chamber in which a gas that absorbs light of a predetermined wavelength is sealed, and into which the laser light is incident; an emitted light amount detection unit that detects the amount of light emitted from the gas cell and outputs an emitted light amount detection signal; and a light source control unit that controls the wavelength of the laser light on the basis of the output light amount detection signal. 提供一种实现了入射到干涉光学系统的激光的波长的稳定化的激光干涉仪。激光干涉仪的特征在于，具备：干涉光学系统，具备射出激光的激光光源，使所述激光彼此干涉；气室，其中封入吸收规定波长的光的气体，所述激光入射到该气室；射出光量检测部，检测从所述气室射出的光的光量，输出射出光量检测信号；以及光源控制部，基于所述射出光量检测信号来控制所述激光的波长。