Sporadic catalytic decomposition because of the presence of Au grains is a significant issue to be clarified in electronic devices. Here, we report the inhomogeneous dissociation of native silicon oxide depending on the electronic structure of Au grains using scanning photoelectron microscopy. Upon annealing, the oxygen atoms dissociated from native SiOx layer out‐diffuses in non‐uniform manner, resulting in oxidize the Au layer. Valence band spectra showed that the spit‐orbit splitting, directly related to the coordination number, differs from site to site. Scanning photoelectron microscopy images show that dissociated SiOx coincides with the regions where low‐coordinated Au resides. These results imply that Au with low coordination number activated the dissociation of SiOx and open new pathway to remove undesirable oxide layer at relatively low temperature. Copyright © 2016 John Wiley & Sons, Ltd.