Background : Oral disease rank first by 60% in Indonesia. One of the bacteria that causes oral disease is Staphylococcus aureus. Staphylococcus aureus is bacteria that causes gingivitis and belong to gram positive, anaerobic. Pineapple (Ananas comosus) is a widely spread plant which can live in highlands as well as in lowlands throughout the globe. Active substances found in pineapple (Ananas comosus) peel have antibacterial effect. Objective : The purpose of this study was to determine the minimum inhibitory concentration and minimum bactericidal concentration of pineapple (Ananas comosus) peel extract with 100%, 50%, 25%, 12,5%, 6,25%, 3,125%, 1,56%, and 0,78% concentrations on Staphylococcus aureus bacteria (in vitro). Method : This study was an in vitro, pure-laboratory experimental.. The subjects in this study were Staphylococcus aureus and pineapple (Ananas comosus) peel extract. Antibacterial effect test was conducted using liquid dilution method on Brain Heart Infusion (BHI) medium and solid dilution method on Triton Soya Agar (TSA) medium pineapple (Ananas comosus) peel extract was serially diluted into some concentrations: 100%, 50%, 25%, 12.5%, 6.25%, 3.125%, 1.56%, and 0.78%. Minimum inhibitory concentration and minimum bactericidal concentration were determined by observing the growth of Staphylococcus aureus on both medium. Result: Minimum Inhibitory Concentration (MIC) was at 1,56%, while Minimum Bactericidal Concentration (MBC) was at 3,125%. Conclusion: Pineapple (Ananas comosus) peel extract was effective in inhibiting and eliminating Staphylococcus aureus.