We have investigated the Au-SrTiO₃(100) interface as a function of the Au evaporation using the photoemission spectroscopy. In the valence band of SrTiO₃, the broad state originating from O 2p electrons and a state from Ti 3d electrons were observed between 3-9 eV and at 1 eV below the Fermi level (E_F), respectively. With increasing the Au evaporation, the decrease in intensity of the state at 1 eV was observed. In the Ti 3p core-level, the decrease of the Ti³⁺ states was observed after Au evaporation. These results indicate that the electrons transfer from the Ti³⁺ states of the SrTiO₃(100) surface to the evaporated Au. In addition, with increasing the Au evaporation, the larger shift of the peak in the Au 4f core-level to lower binding energy side was clearly observed as compared to that of the Sr 4p, O 2s, Ti 3p, and Sr 3d core-levels. Based on the results of the photoemission spectroscopy of the valence band and core-levels, we will discuss the electronic structures of the Au-SrTiO₃(100) interface.