An optical fiber for Raman amplification amplifies a signal light with a pumping light. A chromatic dispersion at a wavelength of 1,550 nm is in a range between -70 ps/nm/km and -30 ps/nm/km. Raman gain efficiency with a pumping light of 1,450 nm is equal to or more than 5 (W.times.km).sup.-1. Nonlinear coefficient at the wavelength of 1,550 nm is equal to or less than 5.0.times.10.sup.-9 W.sup.-1. Zero-dispersion wavelength is neither at a wavelength of the signal light nor at a wavelength of the pumping light. Cut-off wavelength is equal to or less than the wavelength of the pumping light.