The present invention provides a highly safe tyrosinase inhibitor having excellent tyrosinase-inhibiting action, and a method for producing the tyrosinase inhibitor. The method for producing a tyrosinase inhibitor comprises the steps of contacting a live earthworm with hydroxycarboxylic acid powder, diluting the resulting mixture with water to adjust the pH to 2 to 5, and then leaving the resulting dilution to stand for 3 to 180 minutes, or contacting a live earthworm with an aqueous solution of hydroxycarboxylic acid having a pH of 2 to 5 and then leaving the resulting mixture to stand for 3 to 180 minutes； followed by washing the live earthworm with water, grinding the washed earthworm, and then freeze-drying the obtained ground product.
