To provide a flexible, highly reliable, and sheet-like power storage device. The power storage device including a flexible substrate; a positive electrode lead and a negative electrode lead over the flexible substrate; and a plurality of power storage elements over the flexible substrate. The plurality of power storage elements each includes a stack body including a sheet-like positive electrode; a sheet-like negative electrode; and an electrolyte therebetween in an exterior body. An edge portion of the sheet-like positive electrode which extends to the outside of the exterior body is electrically connected to the positive electrode lead through a positive electrode tab provided for the exterior body. An edge portion of the sheet-like negative electrode which extends to the outside of the exterior body is electrically connected to the negative electrode lead through a negative electrode tab provided for the exterior body.