Provided are a silicon oxide-carbon composite, a method of preparing the same, and an energy storage device containing the same. In the method of preparing a silicon oxide-carbon composite, a reaction solution containing an organic solvent including an aromatic compound is provided. Crystalline carbon structures are formed by generating plasma in the reaction solution. A slurry is formed by adding silicon halide and a polyol in the reaction solution in which the crystalline carbon structures are dispersed. The slurry is separated from the organic solvent and subjected to thermal treatment.