A method for manufacturing a sealed electric storage device comprising: a step for preparing a bottomed exterior can for storing a group of electrodes; a step for preparing a sealing plate having a peripheral portion corresponding to an opening of the exterior can, the sealing plate having a first cutout on one surface of the peripheral portion to engage an edge of the opening of the exterior can, and having a tapered second cut-out on another surface of the peripheral portion; a step for closing the opening of the exterior can using the sealing plate by causing the first cutout to engage the edge of the opening of the exterior can; and a step for welding together the edge of the opening of the exterior can and the peripheral portion of the sealing plate by directing a laser beam onto the boundary between the edge of the opening of the exterior can and the peripheral portion at an angle of 15 degree to 75 degree with respect to the direction of thickness of the sealing plate.