A permselective membrane reactor is provided, including a reactor tube having a gas inlet at one end and a gas outlet at the other end thereof. A separator tube is disposed in the reactor tube and has a permselective membrane selectively permeable to hydrogen on a surface thereof and a discharge outlet for passing separated gas through the permselective membrane. The permselective membrane reactor also includes a layer comprising a reforming catalyst that promotes reforming of ethanol, so that .beta., defined by the following equation, is in a range of 0.05 to 20: .beta.=a/b wherein a denotes the volume of the reforming catalyst layer [cm.sup.3], and b denotes the area of the permselective membrane [cm.sup.2].