Abstract: A wavelength control method in a laser apparatus including a wavelength actuator configured to cyclically change the wavelength of pulse laser light output in the form of a burst includes reading data on a wavelength target value, determining from the data a first target wavelength and a second target wavelength shorter than the first target wavelength, and setting wavelengths of at least one first-period long wavelength pulse and at least one first-period short wavelength pulse contained in a first period at a start of a burst to a first set wavelength shorter than the first target wavelength and a second set wavelength longer than the second target wavelength, respectively, by using the first target wavelength and the second target wavelength to control the wavelength actuator.