The response function of the front-illuminated CCD, like SIS on ASCA, can be devided into three parts: the gate structure transmission, the absorption efficiency in the depletion region and the charge spreading after the photo-absorption. These effect depend on both the incident X-ray energy and the landing posion of the X-ray inside the CCD pixel. Then, the measurement of the X-ray efficiency within the pixel is important for the response function of the CCD. By using a new technique, we performed an experiment using the SIS CCD chip in the GSFC in order to measure how the various types of events are formed.