PURPOSE: To produce a bipolar membrane having a small potential drop at a high current density, a high current efficiency and good mechanical strengths by laminating an anion exchange resin layer with a specified intermediate layer and a cation exchange resin layer.

CONSTITUTION: A sulfonic acid derivative monomer in which the sulfonic or sulfonate groups are made hydrophobic with a hydrophobic compound of the formula: (CnH2n+1)m-NH(4-n)-Z (wherein (n is 3-10; (m) is 1-3; and Z is an anion) and/or its polymer is mixed with a monomer suitable for introducing anion exchange groups and a monomer containing a crosslinking agent, and the obtained mixture is polymerized to form a membranous object. This object is immersed in a 0.05-0.5 N aqueous NaOH solution to convert the hydrophobic sulfonic or sulfonate groups into hydrophilic ones, and then reacted with an amine to introduce anion exchange groups to obtain an intermediate layer 2. An anion exchange resin layer 1 is laminated with the intermediate layer 2 and a cation exchange resin layer.