Abstract: In this study, we therefore assessed the effects of S. japonicus on melanogenic protein expression of murine B16 melanoma cells. We obtained an S. japonicus extract by treatment with 80% EtOH and then successively partitioned it with n-hexane, CH2Cl2, EtOAc, BuOH and water. Present results indicated that the EtOAc fraction of the S. japonicus extract (SJE) was effectively inhibited melanogenesis in murine B16 melanoma cells. We performed western blotting for melanogenic proteins to elucidate the mechanism of the effect of SJE on melanogenesis. SJE inhibited the expression of tyrosinase, Tyrosinase-Related Protein (TRP)-1 and TRP-2. We also confirmed that SJE decreased the protein level of melanocyte-specific isoform of Microphthalmia-Associated Transcriptional Factor (MITF), leading decreased expression of tyrosinase and tyrosinase-related genes in the B16 melanoma cells. To test the applicability of SJE to the human skin, we used MTT assay to assess the cytotoxic effects of SJE on human keratinocyte HaCaT cells. The SJE exhibited low cytotoxicity at 20 μg mL-1. To test the applicability of S. japonicus as a cosmetic material with regard to its irritant or sensitization potential, we also performed human skin primary irritation tests, which showed no adverse reactions with S. japonicus usage. Hence, we suggest that S. japonicus be considered as a potential anti-melanogenic agent and may be effective for topical application for treating hyperpigmentation disorders.