This invention makes it a subject to provide the pigmentation prevention or improvement agent which has a novel mother nucleus, and the skin external preparation containing the said component. Provided is a pigmentation preventing or improving agent comprising a compound represented by the following general formula (1), an isomer thereof and / or a pharmacologically acceptable salt thereof, and a skin external preparation containing the component. This solves this problem. (1) [wherein R 1 represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, and R 2 represents a hydrogen atom or an unsubstituted or substituted substituent having 1 to 1 carbon atoms. 8 represents an aliphatic hydrocarbon group, an aromatic group having 5 to 12 carbon atoms, a polycyclic fused aromatic group or a heterocyclic group, and R3 is an unsubstituted or substituted aromatic group having 5 to 15 carbon atoms. Represents a group, a polycyclic fused aromatic group or a heterocyclic group, n represents an integer of 1 or 2, and m represents an integer of 0 to 3. ]本発明は、新規母核を有する色素沈着予防又は改善剤、並びに、当該成分を含有する皮膚外用剤を提供することを課題とする。下記一般式（１）に表される化合物、その異性体及び／又はそれらの薬理学的に許容される塩よりなる色素沈着予防又は改善剤、並びに、当該成分を含有する皮膚外用剤を提供することにより、本課題を解決する。（１）[式中、Ｒ1は、水素原子、炭素数１～８の直鎖又は分岐のアルキル基を表し、Ｒ2は、水素原子、若しくは、無置換の若しくは置換基を有する、炭素数１～８の脂肪族炭化水素基又は炭素数５～１２の芳香族基、多環縮合芳香族基又は複素環基を表し、Ｒ3は、無置換の若しくは置換基を有する、炭素数５～１５の芳香族基、多環縮合芳香族基又は複素環基を表し、ｎは、１又は２の整数、ｍは、０～３の整数を表す。]
