PURPOSE: To make it possible to discover even a minute aperture such that foreign matter is caught in from the inside, by blowing high pressure air in a pressure container in which an article to be inspected was sealed hermetically and communicating the hermetically sealed chamber of the article to be inspected with the outside of the container through an air outlet.

CONSTITUTION: A clamp 14 is detached to open an opening and closing lid 3 and an article 10 to be inspected is put in a main body 2. One inlet of the hermetically closed chamber 11 of the article 10 to be inspected, for example, an inlet 15 is closed by a plug 17 and a pipe 8 is connected to the other inlet to be led out to the outside from an air outlet 7. A seal mechanism is applied between the outlet 7 and the pipe 8. Subsequently, the opening and closing lid 3 is closed and the clamp 14 is hooked to close the main body 2 by tightening screws 14a. Succeedingly, when a compressor 6 is operated to introduce high pressure air under pressure from an air press-in port 4 through a pipe 5, if a small aperture is formed to the wall of the article 10 to be inspected, air is invaded in the hermetically sealed chamber 11 from said aperture. When the small aperture is clogged with foreign matter from the inside, said foreign matter is removed by air pressure. After this state is held for a predetermined time, the article 10 to be inspected is taken out to be immersed and air is sent thereinto from the pipe 8. Whereupon, because air bubbles are issued from the small aperture part, the position of said aperture can be determined.