The leaf extract of Ligularia stenocephala showed the highest anti-platelet aggregating activity in large numbers of edible and herbal plants. The active fraction fractionationed from L. stenocephala extract by using preparative HPLC inhibited the platelet aggregation up to above 80% and its blood coagulating time (PT and APTT) also showed similar effect to aspirin (0.2 ${mu}g/mL$), known as an anti-thrombus compound. Two antithrombus active compounds were purified and identified as 3,5-dicaffeoylquinic acid and 3,4-dicaffeoylquinic acid, respectively, on the basis of NMR and FAB-MS spectroscopic data. Two active compounds has not only antiplatelet aggregating activity, but also has anticoagulating activity.