PURPOSE: To produce the title substance efficiently at a high yield with simple and convenient equipment without producing any by-product.
CONSTITUTION: In the process for producing the title substance by immersing a polymn. electrode (3) and a counter electrode (2) in a polymn. liq. (7) contg. a polymerizable monomer, allowing electric current to flow through the electrodes (3) and (2), and thereby electrolytically polymerizing the monomer to precipitate the substance on the electrode (3), a partition through which ions can pass but air bubbles cannot is installed between the electrodes (3) and (2) and the electrolytic polymn. is carried out while forcing the liq. to flow through the partition and simultaneously peeling the substance precipitated on the electrode (3) away from the electrode (3) to float the substance in the liq. (7).