We have fabricated Pd nanoparticles (NPs) with clean surface and revealed the adsorption reaction of dimethyl sulfide (DMS) on Pd NPs/Ni(111) surface depending on the amount of deposited Pd NPs using in-situ X-ray Photoelectron Spectroscopy (XPS). As a result of XPS, DMS does not decompose on Ni(111) and bulk Pd surface. However, DMS dissociates into methanethiolate (MT; CH3S-) and atomic S on Pd NPs/Ni(111). It is found that the activity of Pd NPs surface is higher than that of bulk Pd surface.