Rhus verniciflua Stokes (RVS) has been used as a food supplement and a traditional herbal medicine. In this study, we prepared various flavonoid fractions (RS, RW1, RW2 and RWE) from a hot water extract of RVS and their influence on male reproductive organs and spermatogenesis were studied in rats which were orally administered 200 mg/kg of them for 8 weeks. All experimental groups did not show any significant changes in body weight and blood clinical chemistry for liver function. Plasma testosterone level was elevated about 3.7, 5.2 and 6.3 folds in RW1, RW2 and RWE groups, respectively. The weights of testes and epididymides tended to increase slightly without the statistical significance in RW2 and RWE. The spermatozoon motility and epididymal sperm concentration were significantly increased (P<0.05) in RWE and RW1, respectively, when compared to the control group. There was no significant difference in histology and apparent shape of testes and epididymides among the control and the experimental groups. Collectively, RWE showed effectively the elevation of plasma testosterone level, spermatozoon motility and the epididymal sperm concentration without the significant increase of testis and epidiymides weights. When the component HPLC profile among the flavonoids fractions of RVS was compared, the ratio of components were only different. These findings suggest that the Rhus flavonoid fraction, particularly RWE, can stimulate the androgen-dependent male sexual function and it can be applied to the material of functional food for enhancing the sexual function.