To fabricate porous and thick alumina films, we prepared an aqueous alumina hydroxide sol containing trehalose. The alumina films were deposited by dip-coating technique on glass substrates and heating at 500 °C. The maximum thickness of the film obtained by one-run dip-coating using the sol containing trehalose was over 1000 nm. The film was an aggregate of alumina particles with a diameter of 20-40 nm and pores were interstices between the particles. The porosity of alumina film can be controlled in the range of 48-65 % by changing trehalose concentration in the dip-coating solution.