Optical fibers (220) are routed over a substrate (210), and an optical fiber wiring board (200) is thereby constructed. A relative refraction index difference &Dgr; of the optical fiber (220) is increased to be greater than a relative refraction index difference &Dgr;0 of a communication-dedicated single mode optical fiber, and a core diameter thereof is increased to be larger than a core diameter of the communication-dedicated optical fiber. Thereby, a mode field diameter thereof is set to be substantially the same as a mode field diameter of the communication-dedicated optical fiber.