This invention provides a compound having an excellent melamine formation prohibiting property and being useful as a whitening agent, and a skin care agent containing such compound. The skin whitening agent of this invention contains the compound represented by the following formula (1), or a pharmacologically acceptable salt thereof, as an effective ingredient: wherein A is C1-6 alkyl, C5-6 cycolalkyl, benzyl, benzylcarbonyl, benzoyl, phenyl, pyridyl, or pyrimidyl； Ra is H, C1-6 alkyl, or C2-6 alkenyl； represents a single bond or a double bond, n= 1 or 2； Y is S or O； R3, R4 is H, C1-6 alkyl, hydroxyl C1-6 alkyl, C2-7 acyl, phenyl, pyridyl, or pyrimidyl etc.； provided that the heterocyclic ring containing Y is a thiazoline ring, R4=Ra=H, X1=X2=CH, and when p=0 or R5 is C1-6 alkyl, at least one of R3 is a group other than C1-3 alkyl.本發明提供一種化合物，以及調配有此化合物的皮膚外用劑。該化合物具有優越的黑色素生成抑制作用，是作為美白劑有用的化合物。本發明的美白劑，係以下列一般式(1)表示的化合物或其藥理學上可容許的鹽作為有效成分。(上式中，A為C1-6烷基、C5-6環烷基、苄基、苄基羰基、苯甲醯基，苯基，吡啶基、或嘧啶基；Ra為H、C1-6烷基、或C2-6鏈烯(alkenyl)基；為單鍵或雙鍵，n=1或2；Y是S或O；R3、R4為H、C1-6烷基、羥C1-6烷基、C2-7醯基、苯基，吡啶基、或嘧啶基；但，含Y的雜環為噻唑啉環，而R4=Ra=H，X1=X2=CH，且p=0或R5為C1-6烷基時，至少有一個R3為C1-3烷基以外的基)。
