Method for bleaching teeth and bleaching agent for teeth

A method for bleaching teeth comprises steps of applying a solution containing nitrogen-deeped titanium oxide powder on a surface of teeth, and irradiating the applied part with light to bleach the teeth based on a photocatalytic action thus produced, and a bleaching agent for teeth suitable for carrying out the method comprises a solution containing nitrogen deeped titanium oxide powder, in which the nitrogen-deeped titanium oxide is preferably a photocatalytic substance having a Ti-O-N structure having a titanium oxide crystalline lattice containing nitrogen and exhibiting a photocatalytic action in a visible light region, the bleaching agent contains preferably 0.01 to 5% by weight of the nitrogen-deeped titanium oxide powder, the nitrogen-deeped titanium oxide powder has a specific surface area of from 10 to 500 m2/g, the solution contains water and/or an alcohol as a solvent, and the bleaching agent further contains preferably 0.5 to 20% by weight of a thickener, 1 to 20% by weight of hydrogen peroxide, and 2 to, 45% by weight of urea peroxide.