Power storage device and producing method therefor

A power storage device includes a lid of a case housing an electrode body and a stopper welded to a liquid inlet circumferential portion of the lid by energy-beam welding to seal the liquid inlet. An annular solidified molten portion made of metal, which has been once molten and then solidified, is positioned on a lid thickwise inside than a lid outer plane of the lid over the entire circumference, and has a surface continuing to an outer annular step surface and a peripheral outward surface and coming closer to the lid thickwise inside from a comparative outer surface on an outer side to a comparative inside surface on an inner side when seen from a lid thickwise direction of these two faces.