Recently, investigation on magnetic refrigerators, especially in the temperature range below-15K has been considerably progressed. By the noticeable works on the magnetic refrigerators for producing superfluid He and for liquefing He gas, it is verified that those refrigerators have very high efficiency. In this review, the present stage of the investigation and development on the magnetic refrigerators will be briefly introduced and the prospect of those efforts will be discussed. First, the principle of the magnetic refrigerators and important problems necessary for development of those are shown. And then, the several examples of the magnetic refrigerators are shown and given brief consideration in connection with the problems discussed first. Finally, the current of the present investigations on the magnetic refrigeration is introduced briefly.
