A novel solid oxide fuel cell (SOFC) type catalytic reactor utilizing partial oxidation of methane (CH4 + 1/20(2) = CO+2H(2)) as internal reforming reaction was investigated in the present study. Large electric power, CO-H-2 mixture with molar ratio of 2, and heat energy were obtained simultaneously by applying LaGaO3 based perovskite as electrolyte of fuel cells. Since LaGaO3 based oxide exhibits fast oxide ion conduction, large electric power was obtained. The electric power was further increased by doping small amount of Co or Fe, whilst the open circuit potential decreased due to hole conduction. In spite of 0.5 mm thickness of electrolyte, a maximum power density and yield of synthesis gas were obtained at 731 mW/cm(2) and 21 % at 1273 K respectively on the cell for which Fe doped LaGaO3 based oxide was used. In addition, partial oxidation of methane only occurred in the cell, since the molar ratio of formed CO and H-2 was always 1/2. Therefore, partial oxidation of methane with SOFC is highly attractive from simultaneous generation of energy and useful compound.