The adsorption behavior of gamma-aminopropyl trimethoxysilane (gamma-APS) on copper foil is investigated by using X-ray photoelectron spectroscopy (XPS). Copper foil is immersed in a diluted aqueous solution of gamma-APS and dried in air. It is found that gamma-APS is adsorbed onto the surface almost without hydrolysis. Further, the depth profile by XPS analysis shows that gamma-APS is not hydrolyzed even in the inside layer. In order to obtain hydrolyzed gamma-APS on the copper foil surface, the foil is freeze-dried as immersed in a diluted aqueous solution of gamma-APS. A hydrolyzed form of gamma-APS is found on the top surface. Further, the presence of a powder is confirmed in the bottom of the flask at the end of the freeze-dry experiment. XPS analysis shows the powder is a linear polymer and produced from the silane coupling agent.