An optical transmission system in which a plurality of optical signals each having a different wavelength are transmitted via a single optical fiber, includes: a first dispersion compensator configured to compensate for wavelength dispersion based on a single wavelength of a plurality of signals transmitted via the optical fiber; a demultiplexer connected to the first dispersion compensator, splitting signals output from the first dispersion compensator into different channels according to their wavelengths, and outputting the same; and a plurality of second dispersion compensators connected to each channel split by the demultiplexer, and compensating for the wavelength dispersion of the mutually different wavelength optical signals.