A method for manufacturing an electrode assembly, in which a plurality of electrodes are stacked, wherein a negative electrode and a positive electrode are sequentially and alternately stacked, and a separator is disposed therebetween is provided. The method includes covering a top surface of an electrode disposed at an n layer (n being a natural number) with the separator, heating the separator covering the electrode disposed at the n layer, stacking an electrode disposed at an n+1 layer on the heated separator, covering a top surface of the electrode disposed at the n+1 layer with the separator, and heating the separator covering the electrode disposed at the n+1 layer. The separator is bonded to the electrode, or the separators are bonded to each other to fix the movement of the electrode, thereby improving stability. Since the separator is not stacked in the width direction, capacity per volume increases.