In a plasma processing apparatus, a check valve is installed close to a refrigerant inlet of a compressor. When performing maintenance of a sample stage, refrigerant collected from a refrigerant flow path is temporarily stored in a flow path section extending from an expansion valve to the check valve, making it possible to perform the maintenance without changing the amount of refrigerant in the refrigerating cycle. With a refrigerant storage tank, a refrigerant supply valve, and a refrigerant discharge valve included in the refrigerating cycle, when maintenance of the compressor, a condenser, or the expansion valve is performed, the refrigerant collected from the refrigerating cycle can be put in use again.