Provided is a novel method that makes it possible to easily sterilize spores and the like in a highly safe manner. A method for producing radicals according to the present invention includes a generation step of generating radicals through photoirradiation of a radical generation source, and the peak wavelength of light used in the photoirradiation is greater than UV wavelengths and 600 nm or less. Also, a method for sterilizing spores according to the present invention includes a treatment step of generating radicals through photoirradiation of a radical generation source and treating spores with the radicals, and the peak wavelength of light used in the photoirradiation is greater than UV wavelengths and 600 nm or less. The peak wavelength is, for example, 405 to 470 nm.