Sulforaphane is a compound widely present in consumed vegetables, particularly broccoli. Previous studies have demonstrated that sulforaphane has many physiological effects including anti-cancer, anti-oxidation, and detoxification. In this study, we found that sulforaphane inhibited melanogenesis and tyrosinase expression. The inhibitory effect of 5 microM sulforaphane on melanogenesis was determined to be equivalent to that of 100 microM arbutin. In addition, sulforaphane induced phosphorylated extracellular signal-regulated kinase (ERK) and inhibited phosphorylated p38. It has been reported that the phosphorylated mitogen-activated protein (MAP) kinase family (ERK and p38) controls tyrosinase expression. Our data indicate that sulforaphane inhibited melanogenesis and tyrosinase expression by affecting the phosphorylated MAP kinase family. These findings indicate that sulforaphane might be an effective skin-whitening agent.