Provided is a tooth-whitening agent which exhibits immediate tooth-brightening and -whitening effects. A tooth-whitening agent which is provided with a composition (A) and a composition (B) in a separate state and which is to be used by applying the compositions (A) and (B) alternately to a tooth, wherein: the composition (A) is a composition which contains 0.1 to 30 mass% of phytic acid or a salt thereof in terms of the acid, which does not contain any polyvalent metal cation, or alternatively contains such cations in a molar amount of less than 0.1 time that of phytic acid or the salt thereof, which exhibits a pH of 4 to 6.5 at 25 C, and which contains a fluoride compound in an amount such that the ratio of the mass of the fluoride compound in terms of fluorine atoms to the mass of phytic acid in terms of the acid [(the amount in terms of fluorine atoms)/phytic acid] is 0.05 or less, or alternatively does not contain any fluoride compound and the composition (B) is a composition which contains one or more selected from among orthophosphoric acid, condensed phosphoric acids and salts thereof in an amount of 0.01 to 15 mass% in terms of the acid and which exhibits a pH of more than 6.5 to 10.5 at 25 C.本發明提供一種對牙之光澤賦予效果及牙之美白效果之速效性優異的牙齒美白劑。本發明係一種牙齒美白劑,其分開具備如下之組合物(A)以及組合物(B),組合物(A)係以酸換算量計含有0.1質量%以上且30質量%以下之植酸或其鹽,且不含有多價金屬陽離子或相對於植酸或其鹽含有未達0.1倍莫耳之多價金屬陽離子,25℃下之pH值為4以上且6.5以下,且以氟原子換算量與植酸之酸換算量之質量比(氟原子換算量/植酸)成為0.05以下之量含有氟化物,或不含有氟化物的組合物組合物(B)係以酸換算量計含有0.01質量%以上且15質量%以下之選自正磷酸、縮合磷酸及該等之鹽中之1種或2種以上,25℃下之pH值大於6.5且為10.5以下的組合物,並且用於將組合物(A)及組合物(B)交替地應用於牙。
