Acquired pigmentary skin diseases such as abnormal melanogenesis, vitiligo, chloasma and inflammatory pigmentation are related to regulate the melanin production. The aim of this study was to investigate the effect of Codonopsis lanceolata on the melanogenesis of HM3KO human melanoma cells biologically. The cells were treated for 5 days with Codonopsis lanceolata at several concentrations. Treatment with Codonopsis lanceolata suppressed melanin contents as a dose dependent manner without cytotoxicity and morphological change. And the extract of Codonopsis lanceolata also inhibited tyrosinase, a key enzyme forming melanin, in a dose-dependent manner. And it did not affect the DOPAchrome tautomerase(TRP-2) activity. These results suggest that Codonopsis lanceolata is a candidate for an efficient whitening agent which supresses melanogenesis by a Raper-Mason pathway.