Abstract: A distributing box for laying a cable duct in the construction field in is sealed, after laying the cable duct, with mortar and then buried in the ground. Accordingly, setting up the distributing box is simplified. Also, underground water must not permeate the distributing box. In the present invention, therefore, a duct laying fixture is constructed includes a box-shaped barrel of a water-expansible elastic material attached to the bellows type cable duct, and a water-expansible sheet which is stuck on the outer surface of the barrel. The barrel includes a duct mounting port in which the bellows type cable duct is mounted. Ribs are formed on the peripheral wall surface of the port to come into close contact with the outer peripheral surface of the bellows type cable duct. A slit permits spreading the barrel. The sheet is stuck on the outer surface of the barrel after the duct has been passed by spreading the barrel.