Porous carbongel beads supporting Co or Ni were prepared to enhance decomposition of phenol in water with ozone oxidation. The carbongel beads were synthesized by carbonization of resorcinol-formaldehyde (RF) gel beads whose diameter was approximately 1 mm. Co and Ni were supported on carbongel beads by impregnation with soluble nitrate salts of Co and Ni followed by thermal decomposition and post-oxidation treatment. In the experiments to decompose phenol, the enhancement effects of the carbongels supporting Co or Ni were observed, in which the degradation rate of phenol with these gels were larger than that with pristine carbongel or without any carbongel. In comparison between Co and Ni, Co showed larger enhancement effect. In these experiments, the concentration of the residual ozone in water was monitored. It was revealed that the residual ozone is significantly reduced when Co was used. In the experiments with varied temperature 5, 15, 25 • C, the phenol degradation rate became the highest when the temperature was 5 • C, while the higher temperature of 25 • C was preferable when a reduced concentration of residual ozone is demanded.