PURPOSE: To easily and rapidly carry out an arrangement work of floor ducts for wiring on a slab and take out the wires without concentrating losses in the slab section.

CONSTITUTION: For arrangement of ducts, before upperside reinforcement rods are arranged, floor ducts are laid down by use of a duct tube and a joint box 12 at the crossing having an opening to take out wires at the upper face. Next, the upper reinforcement rods are arranged to place the slab concrete. The floor duct member is composed of a flexible duct 11, the joint box 12 at the crossing having the opening for connection of ducts and the opening for taking out wires, and a support saddle 13 to hold the intermediate position of the ducts 11.