Provided is an optical wavelength coupler using a multi-mode interference. The optical wavelength coupler is a planar waveguide type optical device that can distribute or couple two optical signals having different wavelengths by using the multi-mode interference. The optical wavelength coupler is suitable for integration and is small-sized. Also, the optical wavelength coupler has a low manufacturing tolerance and a low loss, and is insensitive to TE/TM polarization.