The area of window was increased in the envelope of building. So the thermal insulation performance of window and the air tightness performance of window were increased by result of much research. But the solar heat gain performance of window differently affects to the energy consumption of building used heating and cooling. A designer(of windows) needs to be careful about selection of window. With this needs, recently the method of measuring of solar heat gain performance of window was proposed. Among the indexes that indicate the solar heat gain performance of windows, solar heat gain coefficient (SHGC) currently receives more attention while shading coefficient (SC) that describes the level of solar shading based on the 3 mm glass was widely used in the past. Solar heat gain coefficient is a ratio that describes amount of solar energy that enters a building through the windows. But in South KOREA, the measuring equipment was proposed by using solar simulator. Also this method was regulated to Korea industrial standard(KS F 9107). The use of solar simulator has some problem that difference between solar simulator and natural sunlight. To solve this problem, this study proposed the measuring equipment about solar heat gain performance of window by use of natural sunlight. And the authors were studied measuring equipment by advanced research. Also authors developed the equipment. Finally, in this paper, the authors have performed the confirmation of the absorber plate performance. By the test results, the authors confirmed that the improved absorber plate could extract heat from solar radiation.