There is disclosed a permselective membrane reactor which efficiently forms hydrogen by use of a water-gas shift reaction and which is excellent in an aspect of manufacturing cost. In a permselective membrane reactor, a permselective membrane is a Pd membrane or a Pd alloy membrane, and a catalyst layer includes a first catalyst layer on the side of the permselective membrane and a second catalyst layer disposed apart from the permselective membrane. The first catalyst layer has a noble metal-based catalyst, and the second catalyst layer has an iron-based catalyst.