Arbutin has been used as a whitening agent in cosmetic products. Melanin, the major pigment that gives color to skin, may be over-produced with sun exposure or in conditions such as melasma or hyperpigmentary diseases. Tyrosinase is a key enzyme that catalyzes melanin synthesis in melanocytes; therefore, inhibitors of the tyrosinase enzyme could be used for cosmetic skin whitening. A recent study has reported that arbutin decreases melanin biosynthesis through the inhibition of tyrosinase activity. However, this inhibitory mechanism of arbutin was not sufficiently demonstrated in skin tissue models. We found that arbutin both inhibits melanin production in B16 cells induced with $alpha$-MSH and decreases tyrosinase activity in a cell-free system. Furthermore, the hyperpigmentation effects of $alpha$-MSH were abrogated by the addition of arbutin to brownish guinea pig and human skin tissues. These results suggest that arbutin may be a useful agent for skin whitening.