An optical printed circuit board system having a tapered optical waveguide is provided. The optical printed circuit board system includes a substrate as a printed circuit board having an electrical circuit and on which an electrical circuit chip is mounted, a system board including an optical bench coupled to the substrate and on which a photoelectrical signal chip electrically connected to the electrical circuit chip through the electrical circuit, an optical device electrically connected to the photoelectrical signal chip, and a first optical waveguide aligned to the optical device for optical coupling and tapered to have a smaller aperture in an output node for outputting the optical signals smaller than that in an input node for inputting the optical signals are mounted, and a back plane including a groove into which the system board is inserted and a second optical waveguide optically coupled to the first optical waveguide and tapered to have a smaller aperture in the output node than in the input node. The input node of the first optical waveguide is optically coupled to the output node of the second optical waveguide or the output node of the first optical waveguide is optically coupled to the input node of the second optical waveguide.