A method for preparing carbon aerogels and carbon aerogels obtained therefrom are disclosed. The method for preparing carbon aerogels comprises: mixing organic starting materials including phloroglucinol and furfural with a solvent capable of dissolving the organic materials in a predetermined ratio to form a sol solution; adjusting pH of the sol solution adequately by using an acidic or basic catalyst, gelling the sol solution at room temperature under atmospheric pressure, and aging the resultant gels; substituting the solvent in thus obtained gels with liquid carbon dioxide, followed by drying in a supercritical state, to form organic aerogels; and pyrolyzing the organic aerogels in an electric furnace under inert atmosphere to obtain carbon aerogels. Particularly, the gels are formed at room temperature in a short period of time by adequately adjusting pH of the sol solution. Therefore, the method provides improved time efficiency and energy efficiency as compared to existing methods for preparing gels. Additionally, the method allows supercritical drying while avoiding a need for an additional solvent substitution, thereby simplifying the overall process. Further, the method enables preparation of carbon aerogels for supercapacitors having a high specific surface area and high capacitance even in the absence of additional activation step.