A holder including a tubular main body that includes a pair of split bodies, and a hinge that couples the pair of split bodies so that the pair of split bodies can be opened and closed, the tubular main body being configured to be inserted into the tube; and a pair of projections that each have a press surface to be pressed against by an ejector pin, and are respectively formed protruding radially outward from outer circumferential surfaces of the pair of split bodies, wherein the pair of projections are formed so that when the pair of split bodies are opened with the hinge used as a pivot point, the pair of projections come into contact with each other before the outer circumferential surfaces of the pair of split bodies come into contact with each other.