The effect of the Pt film thickness, in the range between 0.5 mu m and 9 mu m, on the polarization characteristics of the anode in a H-2-H2O gas mixture was studied using a fixed film Pt electrode at around 1273 K. The smaller interface resistance and the smaller DC overvoltage were obtained from the thinner Pt film. It was considered that the effect of the Pt film thickness is due to structural change of the Pt film with the thickness based on a model fitting. The anodic current was proportional to P-H2(1/4) but not affected by P-H2O. This agreed with those obtained at the lower temperature.