[Problem] To provide an oxidizer-containing composition and a method for stabilizing an oxidizer with which it is possible to improve the stability of an oxidizer. [Solution] This oxidizer-containing composition is characterized by: containing (A) a stannate, (B) an aminocarboxylic-acid-based chelating agent, and (C) an acid； the mass ratio of the component (B) content to the component (A) content being 0.01-35； and the pH being 2-5. Furthermore, (D) a cationic surfactant, (E) a polyoxyethylene alkyl ether nonionic surfactant, or (F) a hydrocarbon may also be combined.
