This paper describes the fabrication of a planar-type methane reformer based on a composite-type oxygen permeable membrane and its reforming properties. The membrane reformer module comprising Of (Ce0.85Sm0.15)O-2-15 vol.%MnFe2O4 and a ferric stainless steel separator with a same thermal expansion coefficient was successfully developed. For the reformer module, high CH4 conversion, CO and H-2 Selectivity of 96%, 84%, and 89% were achieved, respectively. Based on an electrical conductivity isotherm, joule heat caused by oxygen permeation in the module was estimated to be approximately 8.4 W. In addition, the effect of ZrO2-doping on the mechanical properties and oxygen permeability of the composite material was investigated. The highest Zr-content sample, (Ce0.85SM0.15)(0.2)Zr0.8O2-15 vol.% MnFe2O4, showed a tetragonal structure. As a result of the crystal structural change, superior mechanical properties of Young's modulus of 337 GPa and fracture toughness of 2.8 MPa m(1/2) were obtained. (c) 2008 Elsevier B.V. All rights reserved.