The aim of the research was to examine the antifungal activity and the most effective concentration of teak bark (Tectona grandis Linn F) extract in inhibiting wood decay fungi Schizophyllum commune Fries. Teak bark was derived from BKPH Ledok, Sambong district, Blora Regency, West Java. The Teak bark made into particle with size pass of 40 mesh and retained 60 mesh. Then one kilogram of teak bark particle was maceration with 10 liter of aquadest. The extract then mixes with potatoes dextrose agar (PDA) with several concentration i.e. 0%, 0.25%, 0.5%, 0.75% and 1% and pour into petri dish. One isolate of Schizophyllum commune was put in the center of PDA in each petri dish then incubated for nine days. The bioactive compound of extract teak bark was evaluation used phytochemical screening. Result of the research showed that teak bark extract at concentration 0.25% and 0.5% has antifungal activity values was 27.98% and 40.38% and categorized as medium inhibition growth of S. commune. Meanwhile at concentration 0.75% and 1% the AFA values was 59.94% and 65.51% categorized as strong inhibition growth of S. commune. The bioactive compounds from phytochemical screening test were alkaloid, flavonoid, terpenoid, fenolik, antrakuinon, and saponin. The extract of teak bark with concentration 0.75% and 1% are the most effective concentrations in inhibiting the growth of wood decay fungi S. commune Fries.Keywords : antifungal, phytochemical screening test, Schizophyllum commune, Tectona grandis