A fiber laser system enables an improved reflection resistance property. The fiber laser system includes fiber lasers (2 through 4) each having a laser medium which is an optical fiber made from silica glass. A difference between respective lasing wavelengths of any given two of the fiber lasers is greater than a wavelength equivalent to a half width at half maximum of a peak deriving from a vibration mode of a planar four-membered ring of a Si—O network structure of silica glass.