To easily sort double container according to its material and to maintain a cold keeping effect for a long time, the double container in which the outside of the inside tubular glass container 2 with a bottom is covered with an outside resin container 3 through a heat insulating space 9 in the condition where the top of the container 2 and that of the container 3 are connected to each other detachably.

In forming this double container, a cold keeping bag 4 filled with a cold keeping agent 10 which expands when frozen and contracts when unfrozen is stored between the bottom of an inside container and the bottom of an outside container, and a gap for a heat insulating space is formed. The bottom of the bag is provided with a raised bottom part 14 by raising its bottom face. When the agent is unfrozen, the ceiling part 12 of the bag and the bottom of the inside container contact or come closer through the gap 16. When the agent is frozen, in order to deform the ceiling of the bag by the expansion of the agent and to tightly contact the ceiling part of the bag with the bottom of the inside container by the deformation, the ceiling part of the bag is formed thinner than the side peripheral part and the bottom part of the bag.