This paper describes a study on surface film formation and hydrogen permeation at stainless steel surfaces under high pressure hydrogen. In order to investigate hydrogen permeation into the steels, exposure tests in high pressure hydrogen were conducted with AISI 316 and 316L stainless steel specimens. To determine the concentration of hydrogen in the specimens and characteristics of surface oxide layer, desorption spectra of hydrogen and water were determined with TDS. In addition, XPS analyses were performed to identify chemical composition of the exposed surfaces. It was found that the permeation of hydrogen through the steel surface was related to the desorption behavior of water, which could be originated from the surface film formed during the exposure to high pressure gas.