PROBLEM TO BE SOLVED: To provide a method for decontaminating an object to be treated by reducing the activity of endotoxin by a simple method. SOLUTION: The decontamination method according to the present invention includes a step (a) of reducing the activity of endotoxin attached to the object to be treated by irradiating the object to be treated with ultraviolet rays having a wavelength of less than 200 nm. .. [Selection diagram] Fig. 1【課題】簡易な方法で内毒素（エンドトキシン）の活性を低下させて、処理対象物を除染する方法を提供する。【解決手段】本発明に係る除染方法は、処理対象物に対して２００ｎｍ未満の波長の紫外線を照射することで、処理対象物に付着した内毒素の活性を低下させる工程（ａ）を含む。【選択図】 図１
