PROBLEM TO BE SOLVED: To provide a sterilization method capable of ultraviolet sterilization with high certainty to bacterial cells to be sterilized low in ultraviolet permeability such as foods or drinks without reducing flavor or quality thereof, capable of practically omitting cleaning operation of an ultraviolet permeable window material in an ultraviolet irradiation device and further less in risk of re-contamination.SOLUTION: By selectively irradiating ultraviolet in a wavelength range of 253 nm to 280 nm surely to bacterial cells to be sterilized in a container from outside of the container through an ultraviolet permeation part after filling the bacterial cells to be sterilized in a container having the ultraviolet permeation part having uniform thickness such as a plastic bag by making a bag from an ultraviolet permeable film consisting of a heat sealing resin for example, the container in which the bacterial cells to be sterilized are filled from completion of the filling to completion of ultraviole
