The invention provides an optical fiber laser apparatus. In the invention, an excitation light source outputs light of a given wavelength. A first optical fiber generates light of a plurality of wavelengths including light of a first wavelength by up-conversion from the output light. Also, a first resonator includes first and second mirrors provided on both ends of the first optical fiber, respectively. The first resonator selects the first wavelength light to output via the second mirror. Further, a second optical fiber amplifies an output of the first wavelength light incident from the first resonator. In addition, the first and second mirrors have higher reflexivity for the first wavelength light than the second wavelength light having higher gain per length of the optical fiber. The first fiber has a length set such that the first wavelength light oscillates preferentially over the second wavelength light.