Abstract: An energy storage device includes a current collector (negative electrode current collector), an insulating member (lower insulating member) that abuts on the current collector, an electrode assembly, and a leading plate (negative electrode leading plate) that connects the electrode assembly and the current collector. The leading plate includes an engaging unit (notch) that engages the insulating member or the current collector, and the insulating member or the current collector includes an engaged unit (projection) that the engaging unit of the leading plate engages.