We have measured a frequency shift of the noncontact atomic force microscopy (NC-AFM) cantilever above Au islands when we scanned the X-ray energy around the Au L-3 absorption edge. We have found a clear peak of the frequency shift just above the Au L-3 absorption edge. This novel phenomenon suggested that the combination of energy-variable X-rays and NC-AFM provides us a new way of nano level chemical mapping of surfaces.