PROBLEM TO BE SOLVED: To provide a new and useful kinesin inhibitor and to provide a composition which is useful for easing, preventing or improving various pigmentation symptoms such as a skin blemish and a freckle.SOLUTION: The kinesin inhibitor includes, as an active ingredient, a wild thyme extract. A pigmentation inhibitor is based on kinesin-inhibiting action. In addition, various compositions (medicinal drug compositions, food compositions and cosmetic compositions) contain the kinesin inhibitor.