The liquid-phase oxidation induced by a gaseous plasma was investigated. The plasma was generated between an electrolytic solution and a tip of anode in contact with the surface of solution by means of contact glow discharge electrolysis (CGDE). Aniline dissolved in a neutral phosphate buffer solution was smoothly oxidized and eventually degraded to inorganic carbon. As the intermediate products, three isomeric aminophenols, of which p-isomer was predominant, were detected as well as some carboxylic acids such as oxalic, formic and malonic acids. It turned out that the decay of not only aniline but also total organic carbon (TOC) obeyed the first-order rate law. Furthermore. the effects of volume of solution and electrolytic current on the reaction rate were discussed in connection with the reaction mechanism and it was proposed that the hydroxyl radical might be the most likely oxidant responsible for the degradation of aniline.