Iron niobate photocatalyst as a new type of photocatalyst was prepared by solid-state reaction of Fe3O4 and Nb2O5 and its activity was evaluated using photocatalytic degradation of methyl orange. Preparation conditions such as calcination temperature and time, and irradiation time were investigated according to photocatalytic efficiencies. FeNb2O6 was produced during calcination below 700 oC and FeNbO4 was produced above 800 oC. Iron niobate with optimum activity could be prepared after calcination at 700 oC for 8 h when Fe:Nb molar ratio was 0.8:1. Methyl orange degradation rate was 72.7% after 180 min of irradiation at photocatalyst concentration of 4 g/l.