Abstract: A digestive tract device is configured to reduce the burden on a living body associated with the adjustment of the length of a tubular portion retained inside the living body and simplify a retention operation after introducing the digestive tract device into the living body. The digestive tract device includes a tubular portion provided with a main body having a through hole extending in the longitudinal direction and a tip opening continuous with the through hole and a folded-back portion formed by folding back the main body in the longitudinal direction, a holding unit which holds the folded-back portion in a folded-back state with the tip opening open, and a retention unit which is provided on the base end side of the tubular portion and retains the tubular portion inside a living body.