Abstract: A power storage device is provided with an upper cover, a cell module and a lower cover. A tab joint portion is locally formed at each of two sides of the cell module to be welded and assembled with a tab. When welded with the tab joint portion, the tab merely needs to be placed horizontally or be slightly at an inclination angle, and one-time bending is performed on an electrical connection part on the tab, so as to be electrically connected to an electrode of the upper cover. Therefore, the situation that a plasticized metal protective film wrapped on the outer edge of the tab or the cell module is easy to crack caused of many times of bending in the prior art can be improved.