PURPOSE: To obtain more accurate, reliable data for only a part to be measured by holding a member to be measured between an air cleaning part and a dust collecting part, and sucking the cleaned air through the member to be measured.

CONSTITUTION: A part of a dust-free film is held and fixed between an air cleaning part 15 and a dust collecting part 18. A connecting part 17 of the dust collecting part 18 is connected to a sucking port 9 of a dust counter. When the dust counter 7 is turned ON, a specified amount of air is sucked with a sucking pump of the counter 7. The sucked external air (b) becomes clean air (a) through an air filter 13 of the air cleaning part 15. The clean air is collected in a dust collecting body 16 through the fabric of a dust-free costume 10. The dust which is generated from the fabric when the clean air passes through the fabric is sucked into the counter 7 through a hose 8 together with the air, and the dust particles are counted. The counted number at this time is the number of the dust particles of the dust-free costume.