This paper describes preparation and methane reforming characteristics of a proto-type reformer based on a composite-type oxygen permeable membrane. The tape-cast membrane of Sm-doped CeO2 and 15 vol% MnFe2O4 composite was combined with ferric stainless steel separator with a same thermal expansion coefficient. For the reformer module, high CH4 conversion, CO and H2 selectivity of 96%, 84% and 89% were achieved, respectively. Based on C, H and O balances, oxygen permeation flux was found to be 5.7 mu-mol/cm2s. Joule heat caused by the oxygen permeation was estimated to be approximately 17.5 W, and this covered most part of heat required for reforming reactions.