An optical transmission apparatus includes a transmitting unit for transmitting an optical signal with a specified wavelength, a multiplexing unit for multiplexing the optical signal with the specified wavelength and an optical signal with a wavelength other than the specified wavelength and outputting the multiplexed signal as a wavelength division multiplexed optical signal, an optical amplifier for amplifying the wavelength division multiplexed optical signal outputted from the multiplexing unit, a level detecting unit detecting a variation of an optical power of the wavelength division multiplexed optical signal inputted to the optical amplifier, and a level adjusting unit for adjusting, when a variation of the optical power of the wavelength division multiplexed optical signal is detected by the level detecting unit, a transmitting power of the optical signal with the specified wavelength transmitted from the transmitting unit so that an output power becomes a level before the variation.