Provided is a bacteriostatic method for suppressing the proliferation of a bacterium while reducing the influence on a human body.
The bacteriostatic method is for suppressing a proliferation of a bacterium in a target region and includes a step (a) for irradiating the target region with ultraviolet light having a main peak wavelength of 200 nm to 230 nm inclusive at an average irradiance equal to or less than DMax (µW/cm2) defined by Formula (1): DMax=9391.1×exp−0.043λ
where λ is the main peak wavelength (nm),
wherein,
when the bacterium is Staphylococcus aureus, the step (a) includes irradiating the target region with the ultraviolet light at an irradiance equal to or greater than 0.4 µW/cm2, and
when the bacterium is a mold, the step (a) includes irradiating the target region with the ultraviolet light at an irradiance equal to or greater than 0.29 µW/cm2.