This note reports an enhancement in the degradation of phenol in aqueous solution by simultaneous use of gas-phase corona discharge and mesoporous carbon gels supporting Ni or Co as catalyst. In this study, a direct-current corona-discharge reactor that consisted of a needle cathode placed above a water film was used. Disk-shaped carbon gel was submerged in the water film under the corona-discharge zone. The degradation rates of phenol by corona-discharge reactor without carbon gels, with plain carbon gels, and with metal-supported (Ni or Co) carbon gels were compared. When Ni or Co was supported on the carbon gel, the phenol degradation was enhanced in this reactor. The degradation of TOC was clearly enhanced by supporting Ni on the carbon gel. Such an effect cannot be realized in the use of TiO2-supported silica gel.