An object of the present invention is to provide a prophylactic or ameliorating agent for pigmentation having a novel scaffold and an external preparation for skin containing the same as a component. The object is achieved by providing a prophylactic or ameliorating agent for pigmentation comprising a compound represented by the following general formula (1), an isomer thereof, and/or a pharmacologically acceptable salt thereof and an external preparation for skin containing the same as a component: [wherein R1 represents a hydrogen atom or a linear chain or branched alkyl group having 1 to 8 carbon atom(s); R2 represents a hydrogen atom, a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 8 carbon atom(s), a substituted or unsubstituted aromatic group, a substituted or unsubstituted polycyclic fused aromatic group, or a substituted or unsubstituted heterocyclic group having a 5 to 12 carbon atoms; R3 represents a substituted or unsubstituted aromatic group, a substituted or unsubstituted polycyclic fused aromatic group, or a substituted or unsubstituted heterocyclic group having a 5 to 15 carbon atoms; n represents an integer of 1 or 2; and m represents an integer of 0 to 3.]