A marked difference in the reaction rate of an azobenzene-based photochromic amorphous molecular material between films prepared by vacuum deposition and spin coating was found, the rate for the vacuum-deposited film being significantly faster compared to spin-coated amorphous film; this result indicates that the microstructures of amorphous films prepared by the above two methods are different from each other, suggesting that the local free volume of the vacuum-deposited film is smaller than that of the spin-coated film.