We measured the incident energy dependence of the relative cross section of both elastic scattering and vibrational excitation of methane molecule physisorbed on the surface of Ag(111) using high-resolution electron energy loss spectroscopy (HREELS). The substrate was mounted on a closed-cycle refrigerator attached on a manipulator for XYZ translation and rotation, and is cooled down to 15K. It has been measured that the elastic cross section shows double dips suggesting the existence of surface resonance.@footnote 1@ At the present experiment with improved resolution, the variation of resonance structure was measured depending on the ambient pressure of CH@sub 4@, which possibly corresponds to the variety of the structure of adsorbed CH@sub 4@ . In addition, the shape of the loss peaks in EEL spectra has a tail which might indicate the rotation of CH@sub 4@ molecule on the surface. @FootnoteText@ @footnote 1@ M. Sakurai, T. Okano and Y. Tuzi, Vacuum 41, 234 (1990).