We evaluated the various cleaning methods of ITO substrates such as aquaregia and RCA, using the organic electroluminescent devices with a structure of ITO/TPD/Alq(3)/LiAl. And the surface morphology of ITO substrates chemically treated in various ways was also investigated using Atomic Force Microscopy (AFM). It was found that in suitably treated device, both current injection and electroluminescent characteristics of the devices were significantly enhanced.