a primary stack manufacturing step in which two first electrodes and a second electrode of the primary stack are alternately stacked with separators therebetween on a top surface of a table so that the first electrodes are disposed at each of an uppermost end and a lowermost end of the primary stack;

a secondary stack manufacturing step in which first electrodes and second electrodes of the secondary stack are alternately stacked with separators therebetween on top of the primary stack at a first end of the primary stack so that one of the second electrodes is disposed at a lowermost end of the secondary stack;

a stack rotating step in which the primary stack and the secondary stack, which are initially disposed on the table, are rotated together at an angle of 180° to change vertical positions of the primary stack and the secondary stack, the stack rotating step comprising gripping the primary stack and the secondary stack together using a gripper, descending the table away from the primary stack, rotating the primary stack and the secondary stack together at the angle of 180° using the gripper, and ascending the table so that the secondary stack is supported on the table; and

a tertiary stack manufacturing step in which first electrodes and second electrodes of the tertiary stack are alternately stacked with separators therebetween on top of the primary stack at a second end of the primary stack opposite from the first end so that one of the second electrodes is disposed at a lowermost end of the tertiary stack.