Abstract: A demolding device that removes a thin-walled part from a mold, the thin-walled part being tubular and having a partially open wall, the demolding device including: contour units that are located in a circumferential direction of the thin-walled part and each of which includes a contact structure that contacts an outer surface of the thin-walled part and moves in a thin-walled surface outward direction extending away from the outer surface of the thin-walled part; and a puller that engages with edges of the partially open wall of the thin-walled part and that applies a load to the thin-walled part, the load including a force component acting in the circumferential direction of the thin-walled part. In response to application of the load from the puller to the thin-walled part, each of the contour units moves the contact structure to keep the contact structure in contact with the thin-walled part.