From catalytic perspective, molecular behavior on topmost surfaces of nano-sized metal(alloy) particles is a key issue. Our experimental approaches for studying catalysis is preparations of well-defined surfaces of metals, alloys, semiconductors by using UHV (MBE) techniques and discussion on molecular behaviors on the well-defined surfaces. We routinely use UHV-MBE, surface vibrational spectroscopies (IR, Raman), SPM (AFM, STM), electron spectroscopy (XPS), electrochemical (EC) voltammetry, etc., and try to clarify dynamic solid surface phenomena on atomic/molecular levels. We believe our research directly links to comprehensive understandings of industrial processes, such as catalysis, thin film growth, electrochemical reaction etc.