We have developed a facile synthetic method for highly water-soluble, hollow carbon nanoparticles with a diameter of ∼1 nm, as a so-called fullerenol. The method was extended to fullerene soot to obtain the corresponding hydrophilic carbon materials, and the products were subjected to IR and elemental analysis. Particle size analysis demonstrated the relatively high dispersion of particles with diameters of ∼70 nm, in water. The surface analysis using FE-SEM showed the difference in morphology between fullerene soot and activated carbon as well as between before and after hydrophilic treatment of the soot with hydrogen peroxide. Moreover, this hydrophilic fullerene soot exhibited high antioxidant activity as compared with fullerenol and C60.