Provided is a light branching optical waveguide including: at least one incident light waveguide (A) optically connected to one end of a multi-mode optical waveguide; and output light waveguides (B) larger in number than the incident light waveguide (A) optically connected to the other end thereof, the light branching optical waveguide being characterized in that: an intensity distribution of light incident from at least one optical waveguide (a) out of the incident light waveguide (A) on the multi-mode optical waveguide at a connecting surface of the incident light waveguide (A) and the multi-mode optical waveguide is asymmetric with respect to a geometrical central axis of the optical waveguide (a); and an extended line of the geometrical center axis of the optical waveguide (a) does not coincide with a geometrical central axis of the multi-mode optical waveguide. Accordingly, it is possible to obtain a low-loss light branching optical waveguide having a reduced branch loss and a reduced variation in branching ratio, and further to obtain a light branching optical waveguide having small wavelength dependence as well as a reduced branch loss and a reduced variation in branching ratio.