In order to establish a design technology for ultrahigh-purity gas piping systems and to implement effective purging for future ultralarge-scale integration (ULSI) fabrication lines, it is necessary to develop highly accurate simulation technology. We have investigated the heat of adsorption and adsorption isotherms with trace moisture concentrations on various stainless steel surfaces as a means to develop highly accurate simulation technology. We observed that the activation energy of desorption varied as of the surface coverage ratio of moisture increased in the range under monolayer adsorption. We investigated the vibration cycle of adsorbed moisture molecules, and observed that the vibration cycle was 2×10^-13s at the adsorbed moisture concentration of 1.4×10¹⁴ molecules/cm² for an Fe₂O₃ surface. The calculated moisture concentration using the Freundlich adsorption isotherm coincided with the measured concentration in the range of about two orders of magnitude as compared to other adsorption isotherms.