We present the surface analysis of (NH4)(2)S-x-treated InGaN using x-ray photoelectron spectroscopy. The native oxide and organic contamination on the InGaN surface can be removed by (NH4)(2)S-x surface treatment. However, the hydroxyl species present on the InGaN surface cannot be removed. Because Ga-S and In-S bonds were formed and N-S bonds were not observed, we deduce that the sulfur atoms would occupy the nitrogen-related vacancies and bond with the Ga and In atoms. The clean surface and surface state reduction caused from the (NH4)(2)S-x surface treatment would be useful for the formation of ohmic and Schottky contacts between the metal and InGaN layers.