The five flavonoids, isoqueritrin, juglanin, astragalin and 2-O-trans-p-coumaroyl astragalin were quantitatively analyzed in the leaves, unripe- and ripe fruits of four Korean Rubus species including Rubus crataegifolius, R. pungens var. oldhami, R. parvifolius, and R. coreanus belonging to the Rosaceae family. The HPLC analysis demonstrated that flavonoids are more abundant in the leaves than in the fruits. In the four Rubus species, ripe fruits generally contained similar or more amount of flavonoids than in unripe fruits. In particular, the quantity levels of total flavonoid (49.81${pm}$0.50 mg/g) and isoquercitrin (35.08${pm}$0.37 mg/g) were highest in the leaf of R. crataegifolius. In addition, the content of the flavonoids were quite low in the unripe fruits of R. coreanus that is most widely used as Rubi Fructus.