A method for autoclave sterilization of an endoscope 2 of the present invention includes the step of making a space, which is defined by the outer side of a channel and an outer covering member of the endoscope 2, communicate with the outside of the endoscope, while at least one end of the channel communicates with the outside of the endoscope 2 and the channel is inserted through the inside 47 of the endoscope. The space 47 and the outside of the endoscope are once brought into the negative pressure. Thereafter, steam is introduced in the space 47 and the outside of the endoscope, and the endoscope 2 is sterilized.
