An optical module mounting method for mounting an optical module including a plurality of light emitting points onto a substrate including an optical waveguide is provided. The method includes mounting the optical module on the substrate such that a surface of the optical module including the plurality of light emitting points faces one end of the optical waveguide; measuring optical coupling efficiency between each of the light emitting points and the optical waveguide; and selecting a light emitting point to be used based on the optical coupling efficiency measurements.