Duct and method for manufacturing same

A method for manufacturing a duct comprising a step of causing molds to suck and form a pair of molten resin sheets to be formed into a tubular duct main body, then disposing a sound absorption member on the resin sheets, and closing the molds, wherein the method has at least one of configurations (A) and (C):

• (A) the molds are configured such that a side edge of the sound absorption member is sandwiched between the pair of resin sheets, the duct main body has an outward protrusion protruding out of the duct main body, the outward protrusion is provided with a rib protruding into the duct main body, and a hollow is formed between the outward protrusion and the sound absorption member;
• and
• (C) a recess is formed in the resin sheet, the sound absorption member is pasted to the resin sheets over the recess, and after the duct is taken out of the molds, the recess is cut off to form an opening, exposing the sound absorption member.