PURPOSE: To make it unnecessary to cover a cover with heat-insulating anti- sweat material so as to simplify constitution, and in addition, to facilitate the attachment and the detachment of the cover by installing the cover to open and close a small chamber in a box.

CONSTITUTION: The small chamber 5 is formed in a frame body 4 together with the frame body 4 at the time of forming an inner door 1, and a lamp 8 is fitted in the small chamber 5. The cover 7 is fitted freely attachably and detachably to the front face of the frame body 4 by being inserted into a locking groove 43 at its lower end and being pushed into the inside of a locking claw 45 at its upper end. Since the central part of this cover 7 projects by using dead space in the box where a commodity rack 10 is arranged, it never obstructs the constitution in the box such as the arrangement of the commodity tack 10, etc. Thus, by installing the cover 7 in the inside of the box in this way, the heat insulation wall outside the small chamber 5 is formed together with the heat insulation wall of the inner door 1, and the cover 7 need not be covered with the heat insulation anti-sweat material, and the constitution is simplified, and in addition, the attachment and the detachment of the cover 7 can be executed without requiring any special care.