PURPOSE: To enable the condition of particles on the inner surface of a duct to be examined after fabrication by projecting a sliding member out of a boss portion, pressing the sliding member against that inside portion of the duct which is opposite to the inner surface of the duct to be examined, bringing the sliding member into close contact with the surface to be examined using a sealant, and examining a filer after a gas is fed and executed.

CONSTITUTION: A main body 1 and a boss portion 6 are inserted into a ultrahigh vacuum duct 15 with the lower end of the boss portion 6 facing a surface 16 to be examined, and air is supplied to an air cylinder 9. Then a sliding member 13 projects out of the upper end of the boss portion 6, together with a sealant 14, and presses that inner surface of the duct 15 which is located opposite to the surface 16 to be examined, and the reaction of the pressure displaces the sliding member toward the main body the surface 16 to be examined, while the sealant 4 is kept airtight respect to the surface 16 to be examined. Under these conditions, a gas is fed into the main body 1 through a tube 3 and a through hole 2 an exhaust pump at the end of an exhaust pipe 5 is operated so that gas is blown to the surface 16 and attaches itself to a filter 7. The number of particles trapped on the filter 7 is checked using a microscope, thereby examining the condition of the surface 16.