ENERGY STORAGE DEVICE

Disclosed is an energy storage device, which comprises an external terminal having any one of positive and negative polarities and including a protrusion and a first terminal; a case having a polarity opposite to the external terminal and including an extension; a substrate disposed to surround an outer circumference of the protrusion of the external terminal through a hole formed at a center thereof; and a connection member located at an upper surface of the substrate and coupled to the first terminal of the external terminal, wherein the first terminal and the substrate are connected by means of the connection member, and the extension is connected to the substrate. Since a positive electrode and a negative electrode of the energy storage device are electrically connected to a substrate having a cell balancing function without a harness or any other member, it is possible to reduce the cost required for preparing the harness or any other member, and it is also possible to improve the economic feasibility and productivity of the energy storage device module by omitting the process of installing the harness or any other member.