Oxygen evolution reaction for alkaline water electrolysis was studied using various mixed metal oxide catalysts. Mixed metal oxide electrodes consisting of RuO2, IrO2, and Ta2O5 with various ratios on a titanium substrate were prepared by spray thermal decomposition. The crystallinity of the synthesized catalyst was investigated via X-ray diffraction, and the oxidation state of each component was determined using X-ray photoelectron spectroscopy (XPS). Surface morphology was investigated by scanning electron microscopy, and the roughness factor was determined by cyclic voltammetry (CV) in 1 M H2SO4. Electo-catalytic activity for oxygen evolution reaction was measured by cyclic voltammetry (CV) in 1 M KOH at room temperature, and it was found to be strongly dependent.on composition of catalyst. Among all electrodes tested, catalyst with a composition of Ru:Ir:Ta = 1:2:2.5 exhibited the highest current density of 100 mA cm(-2) at 1.67 V, corresponding to an overpotential of 0.44 V.