To solve the problem of a current air intake duct that it is impossible to twist the duct formed by compression molding around an axis vertical to a plane, in which two flanges exist, due to the rigidity thereof when connecting two semicircular cylindrical bodies to each other by welding both ends of the two semicircular cylindrical bodies formed along two flanges projected from outer surface of the two semicircular cylindrical bodies.

This air intake duct 1 made of a non-woven material formed by thermal molding has flanges 6, 7, 8 and 9 projected from the outer surface of the duct in parallel with the longitudinal directional axis of the duct. A part 4 of the duct is formed into a first bellows, and the part 4 has the two longitudinal flanges 6 and 7 opposite to each other in the radial direction along the fist radial direction D2. The air intake duct also has at least one second bellows-shape part 5 having the two longitudinal flanges 8 and 9 opposite to each other in the radial direction along the second radial direction D3 of the duct. The direction D3 is angled at more than zero, especially at 90 degrees, relative to the direction D2 of the two flanges 6 and 7 formed in the part 4.