There is provided an ion exchange membrane electrolyzer, wherein at least one electrode (8) is energized by coming into contact with plate spring bodies formed on the electrode side of an electrode holding member forming a space with an electrode chamber partition bonded to a plate-like electrode chamber partition by a strip-like bonded portion (13), the electrode has a connected portion (83) extending from a plane (82) parallel to the ion exchange membrane toward the electrode holding member side in a direction perpendicular to the electrode plane, the connected portion is provided with an engaging opening (85) extending in a direction perpendicular to the electrode plane, and the engaging opening engages with an engaging member (84), permitting the electrode to move in a direction perpendicular to the electrode plane within the displacement range of the plate spring bodies.