An opening long in the longitudinal direction of a duct wall is formed. The whole of the opening is covered with non-woven fabric, and the lateral width of the opening is set to be not shorter than {fraction (1/20)} of the circumferential length of the duct wall. Alternatively, a porous member is thermally welded with the head of an opening of a small cylindrical portion projecting from the duct wall of a duct body 1, while the duct body is prevented from deformation. In a method for manufacturing the air take duct, a high-melting molded piece is brought into contact with a hot plate so as to be heated. A low-melting molded piece is disposed at a distance from the hot plate so as to be heated by radiation heat from the hot plate.