The present invention provides a whitening agent containing lyoniresinols as whitening active ingredient. The whitening agent of the present invention is useful as a food, a drink, a cosmetic or a pharmaceuticals for preventing or treating the symptom of melanin sedimentation.本發明之目的為提供含有里奈絲醇(lyoniresinol)類作為美白有效成分之美白劑。本發明之美白劑可用於作為預防或治療黑色素沉澱之飲食品、香粧品或醫藥品等。