PROBLEM TO BE SOLVED: To provide a double tube, even when an inner tube body is distended in cryopreserving a specimen, capable of suppressing a gap between the inner tube and an outer tube from being outward communicated to each other.SOLUTION: A double tube 1 is for cryopreserving a collected specimen. The double tube 1 includes: a bottomed inner tubular body 11 for putting the collected specimen therein； a bottomed outer tubular body 12 in which the inner tubular body 11 is inserted so as to form a gap toward the inner tubular body 11 and which is attached to the inner tubular body 11 so as to tightly close an opening side of the gap； and a plug member 3 for tightly closing the inside of the inner tubular body 11. A lower face 11g of the inner tubular body 11 comes into slide contact with a bottom face 12d of the outer tubular body 12, where the diameter of the bottom side of the inner tubular body 11 is reduced compared with that in the opening side of the inner tubular body 11.SELECTED DRAWING: Figure 2
