A method of adjusting the optical axis of an optical waveguide element which can improve a manufacturing yield of the optical waveguide element, an alignment yield between the optical waveguide element and an input waveguide means, etc. and can equalize the branch ratio in a Y-branch waveguide; and an optical waveguide element which can be made compact and also M inhibited from complication in structure by using this method. The optical waveguide element (5) formed on a substrate comprises at least a linear waveguide (6) and a Y-branch waveguide (7) branched from the linear waveguide. The method of adjusting the optical axis of the optical waveguide element (5) when connecting the optical waveguide element (5) and an input waveguide means (3) for inputting a light wave into the optical waveguide element (5) is characterized in that a wide band light or two or more sing wavelength lights (light sources (1, 2)) having a different wavelength are inputted into the linear waveguide via the input waveguide means (3) and then the optical axes of the optical waveguide element (5) and input waveguide means (3) are so adjusted that light waves (10, 11) output from individual branch arms (8, 9) of the Y-branch waveguide may have nearly identical light intensity.