Abstract: A material to be dehydrated wrapped in a semipermeable sheet is dipped in a dehydrating solution to cause part of water contained in the material to be absorbed into the dehydrating solution to dehydrate the material, and the water-absorbed dehydrating solution is cooled and concentrated to adjust its temperaure and concentration, and sterilized as needed, to be used repeatedly for the dehydration treatment, thereby dehydrating a large amount of material to be treated without changing the quality of the material under consistent conditions with enhanced economy and efficiency.