A Raman amplifier includes: a pump light generator that provides a plurality of pump light beams with different wavelengths for an optical transmission medium; a gain monitor that monitors an average Raman gain in the optical transmission medium; a storage unit that stores ratio information indicating a ratio of power of the plurality of pump light beams for a specified gain characteristic with respect to an average Raman gain in the optical transmission medium; and a controller that controls the power of the plurality of pump light beams based on the average Raman gain monitored by the gain monitor and the ratio information.