When daylighting into a building interior, this daylighting structure attenuates the brightness of a setting sun or a winter-time incoming light of small elevation angles, and causes the incoming light to be diffusely emitted toward the ceiling surface or into a deep portion of the indoor space domain regardless of the elevation angle thereof. An incoming light (E20) of 20° in elevation angle is caused to be diffusely emitted toward the ceiling surface on the internal upper side of the building through the refraction and reflection actions mediated by a light-transmitting material mounted in a horizontal direction opening of a wall. The light-transmitting material comprises: an outdoor region curved surface wherethrough the incoming light is refracted and let into the interior of the light-transmitting material in a focused form; a lower side reflection surface internally reflecting the refracted incoming light; and an indoor region curved surface wherefrom the internally reflected light is refracted and emitted toward the ceiling surface in a diffused form. Also disclosed are the installation wherein the light-transmitting material is inclined from the illustrated horizontal state, and the installation of a plurality of the light-transmitting materials, each in upper and lower directions and left and right directions.