In the middle of the effort of the energy consumption reduction in buildings, the area of window at building was increasing according to the view of exterior and the method of construction. The insulation performance of window is low than the building envelope and the solar heat gain performance affects the building energy consumption of heating and cooling. Many efforts to improve the window performance have been made. The method how to verify the window performance was also proposed. This method helped designer to choose of type of window and performance of window. The solar heat gain performance test method by the use of solar simulator was developed. But the measuring equipment about solar heat gain performance of window by use of natural sunlight was not utilized. This study proposed the measuring equipment about solar heat gain performance of window by use of natural sunlight.