Abstract: A first optical waveguide having at least a core layer with a refractive index ncj and a second optical waveguide having at least a core layer with a refractive index nck are arranged to oppose their end surfaces, and at least any one end surface of the first optical waveguide and the second optical waveguide is formed by the etching, and the end surface formed by the etching is covered with a coating medium with a refractive index nij or nik that is equal to a refractive index ncj or nck of the core layer that is exposed from the end surface.