The characterization of electroless Ni-iMo-P/SnO3/Ti electrodes with heat-treatment for oxygen evolution was investigated in 1 M KOH solution. The structures of the electrodes changed significantly with heat-treatment, and the surface; state was different from that of those without treatment. AC impedance measurements showed that the electrode prepared from [Mo2+] = 0.01 M bath possessed the best performance, as evaluated from the value of 1/R(ct). The electrochemical characteristics were found in relation to the morphology and the structure of the electrodes.