Provided is a sterilization method capable of performing ultraviolet sterilization with high reliability on, for example, an object to be sterilized having a low ultraviolet transmittance, such as foods and beverages, capable of substantially eliminating a cleaning operation for an ultraviolet transmissive window material of an ultraviolet irradiation apparatus, and having low risk of recontamination.;In the sterilization method, for example, when an ultraviolet transmissive container such as a flexible bag made of an ultraviolet transmissive film of a heat-sealing resin is filled with an object to be sterilized and is then irradiated with ultraviolet light from the outside of the container to perform sterilization on the object to be sterilized, the container filled with the object to be sterilized is air-tightly sealed during a period from the end of the filling to the end of the ultraviolet light irradiation, or the ultraviolet light irradiation and the sealing are performed under an identical sterile envi
