An electrode assembly comprising: a plurality of electrodes (110, 120) arranged side by side in one direction; and a separator formed in a zigzag shape and configured to insulate the plurality of electrodes from each other, wherein each of the plurality of electrodes (110, 120) includes: an electrode collector foil (112,122), and an electrode active material layer (114,124) provided on both surfaces of the electrode collector foil, the separator includes: a plurality of intervening portions, each of which is interposed between a pair of electrodes adjacent to each other in the one direction; an upper folded portion which connects an upper end of one intervening portion of the plurality of intervening portions and an upper end of another intervening portion of the plurality of intervening portions which is adjacent to the one intervening portion on one side of the one direction; a lower folded portion which connects a lower end of the one intervening portion of the plurality of intervening portions and a lower end of another intervening portion of the plurality of intervening portions which is adjacent to the one intervening portion on the other side of the one direction; and an outermost covering portion which collectively covers the upper folded portion and the lower folded portion, at least one of the upper folded portion and the lower folded portion is welded to the electrode collector foil of the electrode, and the lower folded portion and the upper folded portion are welded to the outermost covering portion. a plurality of electrodes (110, 120) arranged side by side in one direction; and a separator formed in a zigzag shape and configured to insulate the plurality of electrodes from each other, wherein each of the plurality of electrodes (110, 120) includes: an electrode collector foil (112,122), and an electrode active material layer (114,124) provided on both surfaces of the electrode collector foil, an electrode collector foil (112,122), and an electrode active material layer (114,124) provided on both surfaces of the electrode collector foil, the separator includes: a plurality of intervening portions, each of which is interposed between a pair of electrodes adjacent to each other in the one direction; an upper folded portion which connects an upper end of one intervening portion of the plurality of intervening portions and an upper end of another intervening portion of the plurality of intervening portions which is adjacent to the one intervening portion on one side of the one direction; a lower folded portion which connects a lower end of the one intervening portion of the plurality of intervening portions and a lower end of another intervening portion of the plurality of intervening portions which is adjacent to the one intervening portion on the other side of the one direction; and an outermost covering portion which collectively covers the upper folded portion and the lower folded portion, a plurality of intervening portions, each of which is interposed between a pair of electrodes adjacent to each other in the one direction; an upper folded portion which connects an upper end of one intervening portion of the plurality of intervening portions and an upper end of another intervening portion of the plurality of intervening portions which is adjacent to the one intervening portion on one side of the one direction; a lower folded portion which connects a lower end of the one intervening portion of the plurality of intervening portions and a lower end of another intervening portion of the plurality of intervening portions which is adjacent to the one intervening portion on the other side of the one direction; and an outermost covering portion which collectively covers the upper folded portion and the lower folded portion, at least one of the upper folded portion and the lower folded portion is welded to the electrode collector foil of the electrode, and the lower folded portion and the upper folded portion are welded to the outermost covering portion.