PURPOSE: To enable to remove the restriction of materials, and further to prevent the disorder of phase, by piling a projecting layer consisting of a prescribed other material on the clad layer whose surface is plane, and piling an optical waveguide layer whose refractive index is larger than that of said clad layer, on said projecting layer.

CONSTITUTION: A clad layer 32 consisting of an SiO2 film is formed on the Si substrate. Subsequently, metallic mask 41 such as chrome, etc. having the opening of a prescribed shape such as a circle, etc. is superposed, molten quartz SiO2 is piled vertically on the surface of the clad layer 32 by means of spattering, and a projecting layer 34 having the spherical surface is formed on the lower part of the opening of a circle, etc. After that, the metallic mask 41 is removed, glass whose refractive index is higher than that of the clad layer 32 is piled on the blad layer 32 having the projecting layer 34 by means of spattering, and an optical waveguide layer 33 is formed.