Abstract: A compact helium gas-refrigerating and liquefying apparatus with excellent properties and high reliability is provided. The apparatus comprises: a neon gas-refrigerating and liquefying circuit system which precools helium gas and comprises a turbo type compressor, heat exchangers, turbo type expansion machines and a Joule-Thomson valve; and a helium gas-refrigerating and liquefying circuit system which receives the precooled helium gas and comprises a turbo type compressor, heat exchangers, an expansion turbine and a Joule-Thomson valve; the former circuit system being constructed to associate with the latter circuit system so as to further cool the precooled helium gas in the latter circuit system by heat exchange therewith.