The partial oxidation reforming method is advantageous to develop highly effective and low-cost products of H₂ gas used for fuel cells. For the partial oxidation, however, large amount of pure O₂ gas are desirable for acceleration of the H₂ production. Electronic and oxygen ionic conductive (mixed-conductive) oxide ceramics can be used to obtain pure O₂ gas, because the mixed conductivity contributes to permeate pure O₂ gas from air at the elevated temperatures. However, high permeation temperature of above 900°C is a problem. Higher temperature for the permeation incurs deterioration of both the ceramics and the steel to support the ceramics. We intend to find out a new mixed-conductive oxide with high oxygen permeation at lower temperatures than 900°C. In this study, we focus the Sr-La-Fe-Co oxides characterized by the intergrowth structures. We have investigated an appropriate condition to prepare Sr_3-xLa_xFeCoO_7-δ ceramics with intergrowth perovskite structure. Then we have investigated microstructures as well as oxygen permeation properties of a dense Sr_2.45La_0.55FeCoO_7-δ ceramics. The oxygen permeation flux of the Sr_2.45La_0.55FeCoO_7-δ ceramics was as high as that of cubic perovskite Sr_0.8La_0.2 Fe_0.8Ga_0.2O_3-δceramics.