PROBLEM TO BE SOLVED: To provide an antibacterial treatment method which exerts antibacterial activity without light irradiation, is stable toward light, radial rays and an agent such as chlorine, and does not decrease antibacterial effect.SOLUTION: The antibacterial treatment method comprises: preparing an antibacterial treatment liquid which has antibacterial activity at least in a dark place, and contains titanium oxide (IV) containing halogen, and a solvent storing the antibacterial treatment liquid in a dark place and bringing the antibacterial treatment liquid into contact with a material to be disinfected and exerting antibacterial activity. In addition, antibacterial properties are imparted to a substance to be disinfected by drying the antibacterial treatment liquid after the antibacterial treatment liquid is deposited on the material to be disinfected. In addition, the antibacterial activity is strengthened by irradiating the antibacterial treatment liquid with light.
