PURPOSE: To dehydrate an org. solvent such as an aqueous alcohol solution of high water content with highly efficient separation capacity by reacting polyvinyl chloride with sodium N-methyldithiocarbamate and forming the reactional product into a film, and reacting the film with a copper ion to form a complex structure.

CONSTITUTION: A dehydrating separation film is obtained by forming a reactional product obtained by reacting polyvinyl chloride with sodium N- methyldithiocarbamate under a mild condition into a film and further reacting the film with a copper ion to form a chelate structure. This film shows water selective permeation to an org. solvent of high water content such as an aqueous alcohol solution. Therefore, this membrane has high dehydration capacity and sufficient durability. Further, the dehydration separation membrane is easily obtained from a general-purpose polymer by modifying reaction and dehydration capacity can be widely controlled by the kind of dithocarbamate and the difference of a degree of substitution.