Mature silkworm of Bombyx mori is known to contain various functional materials. However, it is too hard to chew or digest for humans when it is cooked or lyophilized. In Korea, the Rural Development Administration recently developed and patented a method for making mature silkworms edible. In this study, therefore, we examined the effects of a larval powder of steamed mature silkworm (SMSP) on skin pigmentation and melanogenesis. For elucidating the depigmenting activity, lightness of a designated site on the murine dorsal skin was measured in vivo. During the experiment, hyperpigmentation was induced on the skin by cumulative exposure to ultraviolet B (UVB) irradiation. At the end of the experiment, melanin production on the skin was visualized by Fontana-Masson staining. Orally administered SMSP of pistachio cocoon strain for at least a month or longer significantly and reduced abnormal pigmentation caused by UVB on the murine dorsal skin. SMSP also showed a potential anti-melanogenic efficacy in modulating UVB-induced hyperpigmentation. Taken together, SMSP was identified as a potential candidate for a novel anti-melanogenic agent, which showed depigmenting efficacy against UVB-induced hyperpigmentation in vivo when administered orally.