A method for manufacturing an electrode assembly, the method comprising: a preparation step of preparing a separator and an electrode; an electrode unit manufacturing step of manufacturing an electrode unit having a structure in which the separator and the electrode are alternately disposed; a pre-sealing step of forming a pre-sealing part in which at least partial regions of the plurality of separators within the electrode unit are attached to each other; and a separator cutting step of cutting a region of the plurality of separators, which comprises the pre-sealing part, characterized in that, in the preparation step, a concave part is formed in the electrode, and a recess part having a recessed shape that is curved toward the electrode is formed in the concave part, the pre-sealing part is formed on at least a portion of the plurality of separators, which covers the concave part of the electrode, upper and lower portions of the electrode unit are pressed by each of an upper pressing device and a lower pressing device at the same time to form the pre-sealing part, each of an upper pressing device and a lower pressing device has a bar shape, one end of each of the upper pressing device and the lower pressing device presses a region of the separator, which is adjacent to the concave part of the electrode, and a curved surface having a curvature corresponding to that of the recess part is formed in one end of each of the upper pressing device and the lower pressing device which press a region of the separator, which is adjacent to the concave part of the electrode, and in the separator cutting step, a concave part and a recess part are formed in the separator, which corresponds to the concave part and the recess part of the electrode. a preparation step of preparing a separator and an electrode; an electrode unit manufacturing step of manufacturing an electrode unit having a structure in which the separator and the electrode are alternately disposed; a pre-sealing step of forming a pre-sealing part in which at least partial regions of the plurality of separators within the electrode unit are attached to each other; and a separator cutting step of cutting a region of the plurality of separators, which comprises the pre-sealing part, characterized in that, in the preparation step, a concave part is formed in the electrode, and a recess part having a recessed shape that is curved toward the electrode is formed in the concave part, the pre-sealing part is formed on at least a portion of the plurality of separators, which covers the concave part of the electrode, upper and lower portions of the electrode unit are pressed by each of an upper pressing device and a lower pressing device at the same time to form the pre-sealing part, each of an upper pressing device and a lower pressing device has a bar shape, one end of each of the upper pressing device and the lower pressing device presses a region of the separator, which is adjacent to the concave part of the electrode, and a curved surface having a curvature corresponding to that of the recess part is formed in one end of each of the upper pressing device and the lower pressing device which press a region of the separator, which is adjacent to the concave part of the electrode, and in the separator cutting step, a concave part and a recess part are formed in the separator, which corresponds to the concave part and the recess part of the electrode.