PROBLEM TO BE SOLVED: To provide a tooth whitening agent excellent in prompt effectiveness of a tooth whitening effect and an effect of providing gloss to the tooth.SOLUTION: The tooth whitening agent contains the following composition (A) and (B) separately in order to apply the composition (A) and (B) to the tooth by turns. (A) is a composition containing 0.1 mass% or more to 30 mass% or less of phytic acid or a salt thereof in terms of acid, not containing a polyvalent metal cation or containing less than 0.1 mole times to the phytic acid or the salt thereof, and having pH of 4.5 or more to 7 or less at 25°C. (B) is a composition containing 0.01 mass% or more to 15 mass% or less of peroxide, and having pH of 4.5 or more to 6.5 or less at 25°C.
