<p>It is intended to provide a method of killing pathogenic microorganisms by which pathogenic microorganisms can be easily killed while maintaining a high safety to the human body and in which neither ultraviolet light nor titanium oxide is employed. A subject substance to be treated is brought into contact with a composition containing an oxidant and then irradiated with light involving rays having one or more wavelengths within a range of 400 nm to 1000 nm. By using hydrogen peroxide or hypochlorous acid as the oxidant as described above, pathogenic microorganisms can be safely and efficiently killed.</p>
