Thin films of ZSM-5 zeolite were prepared on the outer surface of an alumina ceramic filter by hydrothermal synthesis at 473 K. Their structure and atomic composition were shown to be the same as those of the corresponding original zeolite using several spectrometric methods : X-ray diffraction, Si-29 magic angle spinning nuclear magnetic resonance and electron probe microanalysis. The acidic properties of the membrane were evaluated using the conventional temperature-programmed desorption spectrum of ammonia. The morphology and thickness of the zeolite film were dependent on the silica source. Water glass is typically used as the silica source in the preparation of powdery ZSM-5 zeolite. A dense zeolite film could be prepared using Na2SiO3 as the silica source, but could not be obtained using water glass as the silica source.