An energy storage device includes a case, an electrode assembly housed in the case, a current collector arranged between the electrode assembly and a lid of the case in Z-axis direction, and an electrode terminal fixed to the lid. The current collector has a terminal connecting portion connected to the electrode terminal and an electrode connecting portion connected to the electrode assembly. The terminal connecting portion and the electrode connecting portion are arranged side by side in X-axis direction intersecting with the Z-axis direction, and a thickness of the electrode connecting portion is smaller than a thickness of the terminal connecting portion.