The steam reforming of methane was studied over a Ni-based electrode-catalyst in a solid oxide fuel cell under open- and closed-circuit conditions. Experiments were performed over a temperature range of 800-850 degrees C and steam/methane ratios of 2-4. The reaction rate was found to be first order with respect to methane concentration. The apparent activation energy was 39 kcal/mol. It was shown that anodic and cathodic polarization of the electrode-catalyst caused nearly no change in its catalytic properties for steam reforming of methane. A method of estimation of the electrode catalytic activity for methane steam reforming based on the open-circuit electrode potential value is proposed. The loading of the Ni-based electrode-catalyst in the solid oxide fuel cell with internal steam reforming of methane is estimated.