A Brayton cycle type refrigerating apparatus using multiple stages of compressors and having a good response without reduction in efficiency due to change in heat load of the object to be cooled is provided. The Brayton cycle type refrigerating apparatus includes on a refrigerant line on which multiple stages of compressors are arranged in series. The apparatus also includes a temperature sensor for detecting heat load of an object to be cooled and a buffer tank provided between a low pressure line and a high pressure line. A flow rate of the refrigerant in the refrigerant line is controlled by controlling opening degrees of valves to adjust the cooling capacity.