To support a duct so as not to be separated from a section steel due to an external force such as earthquake.

A base part 31 of a slip-lock member 30 being sandwiched between an under surface of a plate flange 6 of an L-section steel 5 and an upper surface of a duct 1 with one surface 32a of a regulation piece 32 of the slip-lock member 30 allowed to abut to one edge of the flange 6 of the L-section steel 5, a press member 23 being placed thereon from above, such that a lower end of its press piece 25 abuts to an upper surface of the flange 6 and that the other end of the base part 31 of the slip-lock member 30 engages with an engagement piece 26, screw parts 21a, 21a of a U-bolt 21 being put through the press member 23 from under, nuts 22 are fastened onto the screw parts 21a, 21a. A slip of the press member 23 with respect to the L-section steel 5 is prevented through the regulation pieces 32, 33 placed erect on both ends of the slip-lock member 30, even if an external force is applied to the duct 1 along its longitudinal direction.