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].
