An electric energy storage device having an inner terminal disposed in a cylindrical metal case and connected to an electrode of a bare cell, the electric energy storage device comprising: a top plate member fitted in a top portion of the metal case, the top plate member having a circular outer circumference, wherein the inner terminal is coupled to a lower portion of the top plate member, wherein the inner terminal includes: a plate-shaped terminal body having a circular outer circumference; at least one electrolyte impregnation hole formed through the terminal body in a thickness direction; a flange located at the outer circumference of the terminal body and extending perpendicular to a plane of the terminal body; and a spacer formed to protrude at a periphery of at least one impregnation hole among the impregnation holes or formed by protruding a part of the plane of the terminal body, characterised in that the terminal body is provided to face the bare cell and coupled thereto to make surface contact, wherein a portion of a side of the metal case corresponding to the inner terminal is formed to have a greater thickness than the other portion of the side, wherein the flange is formed to have a lower height in comparison to the height of the thick side of the metal case, and wherein a beading portion is formed at the metal case by beading a part of a side of the inner terminal at a portion corresponding to the flange so that the beading portion is closely adhered to the flange when the flange is deformed, and the inner terminal is secured and fixed by means of the beading portion. a top plate member fitted in a top portion of the metal case, the top plate member having a circular outer circumference, wherein the inner terminal is coupled to a lower portion of the top plate member, wherein the inner terminal includes: a plate-shaped terminal body having a circular outer circumference; at least one electrolyte impregnation hole formed through the terminal body in a thickness direction; a flange located at the outer circumference of the terminal body and extending perpendicular to a plane of the terminal body; and a spacer formed to protrude at a periphery of at least one impregnation hole among the impregnation holes or formed by protruding a part of the plane of the terminal body, characterised in that the terminal body is provided to face the bare cell and coupled thereto to make surface contact, wherein a portion of a side of the metal case corresponding to the inner terminal is formed to have a greater thickness than the other portion of the side, wherein the flange is formed to have a lower height in comparison to the height of the thick side of the metal case, and wherein a beading portion is formed at the metal case by beading a part of a side of the inner terminal at a portion corresponding to the flange so that the beading portion is closely adhered to the flange when the flange is deformed, and the inner terminal is secured and fixed by means of the beading portion. a plate-shaped terminal body having a circular outer circumference; at least one electrolyte impregnation hole formed through the terminal body in a thickness direction; a flange located at the outer circumference of the terminal body and extending perpendicular to a plane of the terminal body; and a spacer formed to protrude at a periphery of at least one impregnation hole among the impregnation holes or formed by protruding a part of the plane of the terminal body, characterised in that the terminal body is provided to face the bare cell and coupled thereto to make surface contact, wherein a portion of a side of the metal case corresponding to the inner terminal is formed to have a greater thickness than the other portion of the side, wherein the flange is formed to have a lower height in comparison to the height of the thick side of the metal case, and wherein a beading portion is formed at the metal case by beading a part of a side of the inner terminal at a portion corresponding to the flange so that the beading portion is closely adhered to the flange when the flange is deformed, and the inner terminal is secured and fixed by means of the beading portion.