In this paper, a natural lighting system composed of a tilted prismatic daylight collector, an outdoor reflector and an indoor diffuse reflector is described. The light emerging from the hypotenuse of the prismatic daylight collector is redirected onto the indoor reflector for natural light illumination. The results of measured illuminances are in agreement with the results of calculation. The prismatic daylight collector not only decreases discomfort glare but also collects daylight for the natural lighting system. The open natural lighting system, which uses less material, can be realized by the detailed analysis of the characteristics of the light emerging from the hypotenuse of the prismatic daylight collector for sunlight incident on the collector.