Abstract: According to the present invention, a pre-cleaning process is performed for removing a physical substance such as blood, mucus or tiny pieces of tissue that are attached to the exterior of the medical device and are inside a duct or a hollow portion. Then, the pre-cleaned medical device is immersed in a chlorine dioxide solution and/or a chlorine dioxide solution is passed through the duct or the hollow portion. Thereafter, the medical device is placed in a chlorine dioxide gas atmosphere and/or a chlorine dioxide gas is passed through the duct or the hollow portion. In this manner, the exterior of the medical device and the interiors of the duct and the hollow portion are deodorized, disinfected and sterilized.