Staphylococcus aureus induces chronic infection in form of biofilm that exists in the host cells and arthroplastic prosthesis surface. In this study, the biofilm formation ability of S. aureus clinically isolated from bacteremia patients, biofilm processing and relationship of resistance to antibiotics, and difference of biofilm formation ability on different prosthetic material surfaces were studied. All of them formed biofilm and especially 6 strains of S. aureus had high ability of biofilm formation. In addition, it was found that some strains with higher biofilm formation ability make more higher polysaccharide layer production. When S. aureus ATCC 25923 forms biofilm, minimal bactericidal concentration (MBC) of biofilm bacteria is more increased than that of the planktonic state bacteria about one thousand folds. Especially, after 6 hours from starting on biofilm formation, the resistance to antibiotics was increased by more than $256{mu}g/ml$ of MBC to every antibiotics and after 8 hours prominent increase (more than $4096{mu}g/ml$) was noted. Biofilm formation after bacterial adherence to plastic cover-slip was increased with time-dependent manner. Microcolonies were formed after 5 hours from a point that bacteria adhere to plastic cover-slip surface and after 6 hours biofilm was diffusely formed on entire surface, and then after 8 hours very thick biofilm was formed. Thicker biofilm was found on cobalt-chromium than titanium surface. These results suggest that titanium alloy materials are better than cobalt-chromium to minimize S. aureus biofilm formation on the arthroplastic material surface. Also, when microcolonies are formed after adherence of S. aureus to the arthroplastic material surface, resistance to antibiotics is starting.