Durability of the novel catalyst system for phenol synthesis by vapor phase oxidation of benzoic acid was investigated in detail. Although an obvious deactivation was observed using the NiO-NiFe2O4-Na2O system, prominent results were obtained by the addition of V2O5 to the catalyst. More than 90% both in phenol selectivity and benzoic acid conversion were maintained more than 100 h. The remarkable enhancement of catalytic performance is considered to be derived from the facilitated reoxidation of active species by V2O5 in its redox cycle.