This study aims to elucidate how the difference in surface roughness of JIS SUS304 influences the amount of adsorbed water as a function of relative humidity (RH). The time-dependent change in the weight of adsorbed water and its saturated value were determined by weighting method. It was found that the amount of adsorbed increased continuously with increasing of RH regardless of its surface roughness. ShorterA shorter time was necessary for the completion of adsorption on the smooth surface was supposed to be attributed to relatively less adsorption energy. Hence, the differences in adsorption were also found as a function of surface roughness, with data showing a great increase after initial adsorption.