An ion exchange membrane electrolyzer includes an elastic body configured to press on a second electrode so as to bring an ion exchange membrane into close contact with electrodes. The elastic body includes a fixed part fixed to one of a base part and the second electrode, and an elastic part that extends from the fixed part, and is configured to press on the second electrode by elastic deformation. The elastic part is formed so as to be plate-like and formed so as to be corrugated along a direction in which it extends, such that a top part on one side is in contact with the base part and a top part on the other side is in contact with the second electrode.