PROBLEM TO BE SOLVED: To provide a method for producing salt by concentrating salt in saline water (sea water and the like) by electrodialysis, which can prevent deterioration of salt concentrating ability during an electrodialysis treatment due to contamination of a membrane by an organic matter.SOLUTION: Provided is a method for producing salt by a concentration treatment by electrodialysis, where there is used a cation exchange membrane which comprises a polyvinyl alcohol-based copolymer containing an anionic polymer segment having an anionic group and a polyvinyl alcohol segment, and has a micro phase separation structure where a domain size (X) is in a range of 0 nm
