To provide a duct structure for a hollow wall, achieving installation even if the center positions of both through-holes are displaced and maintaining the airtightness of a hollow space regardless of the deformation of the through-holes and the magnitude of the diameters thereof.

In this airtight dust structure for the hollow wall, a through-duct member composed of a tube 1, center spacers 2, 3 and end pressing members 8 is mounted in the through-holes a, b formed in the internal wall material A and external wall material B of the hollow wall. The tube 1 is composed of an expandable portion 4 formed with recessed and projecting portions, a front flange 6 and a rear flange 5 provided on both sides of the expandable portion, and an insertion guide 7 projecting from the inner periphery of the front flange 6. The center spacers 2, 3 are arranged on the outer peripheral surface of the insertion guide 7. In each of the end pressing members 8, a cylindrical portion 9 provided with an engagement portion 10 fitted into the tube 1 is formed with a pressing flange portion 12. The tube 1 provided with the center spacers 2, 3 is inserted into the through-holes while being deformed, and the projecting portion of the insertion guide 7 is cut. The end pressing members 8 are inserted from the outside of the rear flange 5 and insertion guide 7.