To suppress the formation of frost, stably and accurately control the operation of an air refrigerant unit, and reduce running cost.

An air flow path 4 is formed between the air refrigerant unit 5 using an expander 9 for depressurizing compressed air to generate cooled air and an inner wall body 3 provided inside a heat insulating outer wall body 2 and formed of a well heat conductive material, and a cooled chamber 1 shut off from the air flow path is formed inside the inner wall body. The cooled air is supplied from the air refrigerant unit directly to the air flow path. The cold of the cooled air in the air flow path is radiated via the inner wall body into the cooled chamber to cool the cooled chamber.