To keep freshness of food when the food is processed at a low temperature by forming a frame by connecting the bottom portions of a first side panel and a second side panel through a bottom panel and blowing cooling air into the frame.

The outer surface of a frame consists of a first side panel 1, a second side panel 2 and a bottom panel 3. An inner cooling air circulating path 4 is formed between the panels 1, 2, 3 which consist the outer surface and panels 35, 36, 37 which consist the inner surface. Air is sucked from a cold storage space into the path 4 through an air sucking port 12. The air is cooled by a refrigerating machine 9 which is accommodated in a lower frame 6, and the resultant cooled air is supplied to the inner cooling air circulating path, followed by blowing the cooled air into the cold storage space through a cooling air blowing port 11. Thus freshness of food can be maintained when the food is processed at low temperature.