There are provided a substrate mounted with a photoelectric hybrid circuit having an optical path conversion mirror structure and optical waveguide wiring by reducing the number of parts and the number of fabrication steps, as well as most effectively implement high-density wiring for an optical connection between the optical waveguide and the photoelectric conversion element or optical waveguide array connector that are formed on the substrate, and a device. An optical waveguide layer 12 stacked on a substrate 10 and formed of a wiring core surrounded by a clad layer 11, and cores 15, 16 having tapered surfaces intersecting the respective wiring cores 13, 14 of the optical waveguide layer 12 perpendicularly are arranged, the tapered surfaces 15a, 16a of the cores 15, 16 having tapered surfaces are buried respectively in the wiring portion cores intersecting perpendicularly, and a first core 13 for turning the optical path of light propagating through the wiring portion core at the first core 15 with a tapered surface, and a second core 14 for turning the optical path of light passed through the first core 15 with a tapered surface at the second core 16 with a tapered surface are arranged alternately.