In the optical connection between multi-layered optical waveguides and photoelectric converting elements or optical waveguide array connectors formed on a substrate, the optical coupling efficiency is to be prevented from degrading due to deviation of the optical axis positions between optical elements and the optical waveguide layers that is caused by a radiation due to a beam expansion or by a deviation of positioning layers in producing the optical waveguides. There are stacked, on a substrate, optical waveguide layers, each of which comprises a clad layer and a core having a higher refractive index than the clad layer, and optical elements formed on the uppermost optical waveguide layer. The optical elements are positioned such that they correspond to the optical path conversion mirrors of the cores of the underlaying optical waveguide layer. The light transmission/reception between the optical elements and the optical path conversion mirrors of the cores of the underlaying optical waveguide layer is performed via the cores of overlying optical waveguide layer.