A thin palladium membrane was formed inside the porous wall of an alpha-alumina support tube of 2.0-mm i.d. and 2.6-mm o.d. by a metal-organic chemical vapor deposition (MOCVD) process in which the reaction temperature was continuously increased. The metal source, palladium(II)acetate, was decomposed in argon under reduced pressure. For a membrane prepared with a maximum CVD temperature of 300-degrees-C, the hydrogen permeance and the selectivity to nitrogen in the range of 300-500-degrees-C were respectively higher than 0.1 mol/(m2.s) and 1000 when the hydrogen pressure in the upstream side was about 0.1 MPa. Repeated temperature changes between 100 and 300-degrees-C revealed that the membrane was resistant to hydrogen embrittlement.