PURPOSE: To prevent a filter medium from being blocked in a short time by fitting adhesive layers in front of the inflow side of the filter medium to adhere and capture dust of a relatively large particle size.

CONSTITUTION: Adhesive layers 1a, 1b are fitted to the surfaces of plural walls fixed at the suction hole side of a body 3 and allowing gas sucked in the body 3 to meander. A filter medium 2 is set at the discharge hole side of the body 3. Since dust of a relatively large particle size are adhered to the adhesive layers 1a, 1b, the filter medium can be prevented from being blocked in a short time.