Desulfurization and denitrogenation of light oils have been investigated on the basis of adsorption of sulfur- and nitrogen-containing compounds on methyl viologen-modified aluminosilicate (MV2+/AS) adsorbent. Sulfur and nitrogen compounds, dissolved in n-tetradecane or xylene solution (model light oil), were adsorbed on the surface of MV2+/AS via the formation of a charge transfer (CT) complex with MV2+ by stirring at room temperature and removed successfully from the oil. Desulfurization of actual light oils, however, failed because aromatic hydrocarbons present in the oils suppress the adsorption of sulfur compounds. On the contrary, adsorption of nitrogen compounds was hardly suppressed, even in the presence of a large quantity of aromatics because of lower ionization potential of the nitrogen compounds. By employing the process, the nitrogen concentrations of actual light oils were decreased successfully to less than 35% of the feed values. The nitrogen compounds, adsorbed on MV2+/AS, were desorbed by stirring in toluene, and the resulting MV2+/AS could be reused for further denitrogenation of light oil.