Abstract: An object of the present invention is to provide an air-conditioning duct unit capable of being made compact when transported to largely reduce the cost of transport inside and outside a building as well as the cost of transportation by a truck. A duct unit A of the present invention has upper and lower wall portions 1 and 3 and right and left wall portions 2 and 4 formed of metal sheets, and spin locks curved into a curled shape, the spin locks being provided on the wall portions 1 to 4 at two side edges of the same along the longitudinal direction. One of the pair of spin locks provided on each adjacent pair of the wall portions is inserted in the other to form one of lock joints 9-1 to 9-4 rotatably. The wall portions 1 to 4 are linked so that the duct unit A can be changed in shape. Consequently, the duct unit can be folded so as to be flattened.