A carbonaceous material used as a polarizable active material in an electric double layer capacitor is characterized in that, when measured by an electron spin resonance method without adding any additives, the obtained peak line width is 2 mT or less, and the peak intensity, which is converted into a number of unpaired electrons per 1 g, is 1×1019 or more. A method for producing the carbonaceous material includes removing residual functional groups from the carbonaceous material so that reactions between the residual functional groups and the electrolytic liquid are suppressed when forming a capacitor.