Daylighting is one of the major elements in architectural design. It also plays an important role in the museums focused on displaying artistic works. Many architects have tried to predict daylighting performances in exhibition spaces during the design process of museums. The aims of this study are to present the design methods using the computer program RADIANCE that is available for the evaluations of daylighting performances in indoor space and to help architects design daylighting systems for better exhibition spaces of museums. For this study, Seoul Museum of Art was chosen and it was evaluated the recommended illuminance and the impacts of direct sunlight under the conditions of overcast sky and clear sky with sun. According to simulation results, they indicated that the alternative toplight system(sawtooth shape) was more effective for daylighting of exhibition spaces than the existing toplight system(pyramid shape) and this study showed a method to evaluate daylighting effects in exhibition spaces with various shapes of toplight systems.