A multichannel 3-stage optical fiber amplifier includes a first amplification unit for amplifying an input multichannel multiplexed signal light, a gain equalization unit for equalizing gains for each channel by causing a different amount of loss for each channel in the amplified signal light having a different gain at each channel by the first amplification unit, and a second amplification unit for amplifying the signal light output from the gain equalization unit. Thus, an equalized gain with respect to each channel wavelength can be obtained by a gain equalization unit placed between two amplifiers. Also, signal-to-noise ratio performance can be improved by removing spontaneous emission noise using a wavelength divider.