An ion exchange membrane electrolyzer is provided, which is characterized in that a current is passed through at least one electrode in contact with a plate spring member formed at a portion of an electrode retainer member parallel with a flat plate form of electrode chamber partition, wherein said electrode retainer member is joined at a belt junction to the flat plate form of electrode chamber partition with a space between them, said electrode is provided with a floating mount means at a portion thereof other than a portion of contact with the plate spring member, and said floating mount means is provided with an engaging portion that is engaged with a fixed engaging member to enable said electrode to move in a perpendicular direction to an electrode surface and in a range of displacement of said plate spring member.