In a laser apparatus, a central wavelength of vacuum ultraviolet laser beams whose bandwidth is narrowed can be maintained at a target wavelength in high precision. This laser apparatus includes a laser oscillator for generating a vacuum ultraviolet laser beam whose bandwidth is narrowed and a reference beam having a spectral distribution of a vacuum ultraviolet band to output both the vacuum ultraviolet laser beam and the reference beam; a wavelength meter for measuring a central wavelength of the vacuum ultraviolet laser beam whose bandwidth is narrowed by using at least one emission light contained in the reference beam as a reference; and a controller for controlling the laser oscillator based upon the central wavelength of the vacuum ultraviolet laser beam whose bandwidth is narrowed, which is measured by the wavelength meter, so as to thereby adjust the central wavelength of the vacuum ultraviolet laser beam whose bandwidth is narrowed to a target wavelength. As a result, this laser apparatus can output the vacuum ultraviolet laser beams whose bandwidth is narrowed and whose central wavelength is maintained at the target wavelength in high precision.