To provide a wiring duct that facilitates mounting of a distribution board.

The roughly cylindrical wiring duct 1 comprises a base 2 of a substantially U-formed, in line with an upper contact 2c open at the front and upper/lower sides and in contact with a ceiling 4, and with a lower contact 2d in contact with the top end of the back base 5a of the distribution board 5; and a cover 3 of substantially a U shape that closes openings, excluding the upper and lower sides of the base 2. The upper contact 2c of the base 2 is made to contact the ceiling surface 4, and the back of the base 2 is made to abut against the wall surface 9 to mount the base 2 on the wall surface 9. The distribution board 5 is mounted, by making the upper end of the distribution board 5 contact the lower contact 2d of the base 2.