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 25ºC, 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 25ºC.Linvention concerne un agent de blanchiment des dents qui présente des effets davivage et de blanchiment. Elle concerne un agent de blanchiment des dents qui est constitué dune composition (A) et dune composition (B) dans un état séparé et qui doit être utilisé en appliquant les compositions (A) et (B) alternativement sur une dent, dans lequel : la composition (A) est une composition qui contient 0,1 à 30 % en masse dacide phytique ou dun sel de celui-ci en termes dacide, qui ne contient aucun cation métallique polyvalent ou bien qui contient ces cations en une quantité molaire inférieure à 0,1 fois celle de lacide phytique ou de son sel, qui présente un pH de 4 à 6,5 à 25 °C, et qui contient un composé fluorure en une quantité telle que le rapport de la masse du compo
