Provided are: a tyrosinase inhibitor having an excellent tyrosinase-inhibiting activity and high safety； and a method for producing a tyrosinase inhibitor. A method for producing a tyrosinase inhibitor, characterized by comprising the steps of: bringing a hydroxycarboxylic acid powder into contact with living earthworm, diluting the resultant mixture with water to adjust the pH value of the resultant solution to 2 to 5 and then holding the pH-adjusted solution for 3 to 180 minutes, or alternatively, bringing an aqueous hydroxycarboxylic acid solution having a pH value of 2 to 5 into contact with living earthworm and then holding the resultant solution for 3 to 180 minutes； washing the living earthworm with water； pulverizing the washed earthworm； and lyophilizing the pulverized product.
