Analysis of flavonoid contents in the fruits of Acanthopanax species (A. chiisanensis, A. divaricatus, A. koreanum, A. senticosus, and A. sessiliflorus) was conducted by high performance liquid chromatography. A Discovery$^{(R)}$ C18 ($4.6{ imes}250$ mm, 5 ${mu}m$) column was used with a gradient mobile phase of water and acetonitrile (90 : 10 to 60 : 40 for 60 min) and UV detection was conducted at 350 nm. The contents of rutin, hyperin, quercetin, afzelin, and kaempferol were 0.063~0.540, 0.494~7.480, 0.584~0.704, 0.388~0.567, 0.190~0.471 mg/g, respectively, in the fruits of Acanthopanax species. Total content of flavonoids in the fruits of Acanthopanax species was highest in those of A. chiisanensis. Furthermore, hyperin was the most abundant compound in the fruits of Acanthopanax species. Consequently, our results demonstrate that the fruits of Acanthopanax species containing flavonoids have promising potential as a new income source of agriculture and industry in medicinal natural products, health supplements, and beverages.