Sunlight attracts attention as an illumination energy. An optical fiber can receive the illumination energy from the sunlight for indoor illuminations. However, it is difficult to supply necessary light as illumination throughout all the daytime because receivable angle of illumination energy is limited to narrow angle. Therefore, in this study, a new technique was proposed that is attaching a scattering medium at the edge of the optical fiber to expand the receivable angle. To calculate an effect of the technique, Monte Carlo method was used for radiation transfer in the scattering medium. As a result, the receivable angle of illumination energy became the 0-80°.