An amorphous silicon carbide (SiC) membrane with H2 permeance of 1.2E-7 mol･m^-2･s^-1･Pa^-1 and excellent H₂/CO₂ selectivity of 2600 at 673 K was successfully synthesized on a Ni-gamma-alumina-coated alpha-alumina porous support by counter diffusion chemical vapor deposition (CDCVD) using silacycrobutane (SCB) at 788 K. The dominant permeation mechanism for He and H₂ in the temperature range 323-673 K was activated diffusion. The SiC active layer was formed in Ni-gamma-Al₂O₃ intermediate layer. The thermal expansion coefficients mismatch between SiC active layer and Ni-gamma-Al₂O₃-coated alpha-Al₂O₃ porous support was eased by the low decomposition temperature of SiC source and membrane structure.