A wavelength division multiplexing optical transmission apparatus for transmitting wavelength division multiplexing optical signals, the apparatus including a plurality of optical transmitting units outputting optical signals having a different wavelength from each other, a plurality of optical intensity modulating units intensity-modulating the optical signals, and a wavelength multiplexing unit multiplexing the optical signals. The plurality of optical intensity modulating units sets the amount of wavelength chirp adapting to each wavelength of the optical signals for the optical signals outputted from each of the plurality of optical transmitting units, and the wavelength multiplexing unit multiplexes the optical signals having the amount of wavelength chirp set respectively and then outputs the multiplexed optical signals.