Gas-phase methane contamination caused from stainless steel (SS) surface by metal-metal friction was investigated by introducing tritium as a tracer of hydrogen atom in the metal surface. The emissions of HT, CH3T, and CH4 were measured by radio-gas-chromatography, and the SS canister containing many small SS balls inside was shaken to reproduce the metal-metal friction. The results indicate that the oxide layer on SS surface is controlling the emission of methane.