Provided is a method for processing an article to be processed, by which it is possible to form an external-air-introduction hole at any desired location on the outer shell of a container. The present invention provides a method for processing an article to be processed, the method including a processing step in which a boring drill having a cylindrical distal end part is caused to spin, a flat surface part and a notched part being provided to the distal end part, and a side surface of the notched part having a blade part; and, while the drill is being caused to spin, the flat part is pressed against an article to be processed, and the blade part is brought into contact with said article, whereby a round hole is formed in said article.
