A cylindrical battery cell assembly, comprising: a plurality of cylindrical battery cells, each cylindrical battery cell having a first electrode terminal formed at a top end and a second electrode terminal formed at a bottom end thereof and arranged to stand up so that the electrode terminal having a same polarity face in a same direction; a cell holder configured to confine the plurality of cylindrical battery cells as a bundle unit; a first electrode connection member located at an upper portion of the cell holder to electrically connect the first electrode terminals; and a second electrode connection member configured to electrically connect the second electrode terminals, wherein the second electrode connection member includes: a second connection portion located at a lower portion of the cell holder and disposed to contact the second electrode terminals; and a rod-shaped second terminal portion extending vertically from the second connection portion through an empty space formed inside the cell holder so that a first end of the rod-shaped second terminal portion is disposed above the cell holder; wherein the cell holder includes unit cell body covers, each unit cell cover having a cylindrical shape so that the plurality of cylindrical battery cells are inserted therein, respectively, wherein the unit cell body covers are arranged in a triangular shape so that circumferential surfaces of neighboring unit cell body covers are attached to each other; wherein the unit cell body covers are provided so that at least three unit cell body covers are integrated, and the empty space is a region surrounded by the at least three unit cell body covers that are in contact with each other. a plurality of cylindrical battery cells, each cylindrical battery cell having a first electrode terminal formed at a top end and a second electrode terminal formed at a bottom end thereof and arranged to stand up so that the electrode terminal having a same polarity face in a same direction; a cell holder configured to confine the plurality of cylindrical battery cells as a bundle unit; a first electrode connection member located at an upper portion of the cell holder to electrically connect the first electrode terminals; and a second electrode connection member configured to electrically connect the second electrode terminals, wherein the second electrode connection member includes: a second connection portion located at a lower portion of the cell holder and disposed to contact the second electrode terminals; and a rod-shaped second terminal portion extending vertically from the second connection portion through an empty space formed inside the cell holder so that a first end of the rod-shaped second terminal portion is disposed above the cell holder; wherein the cell holder includes unit cell body covers, each unit cell cover having a cylindrical shape so that the plurality of cylindrical battery cells are inserted therein, respectively, wherein the unit cell body covers are arranged in a triangular shape so that circumferential surfaces of neighboring unit cell body covers are attached to each other; wherein the unit cell body covers are provided so that at least three unit cell body covers are integrated, and the empty space is a region surrounded by the at least three unit cell body covers that are in contact with each other. a second connection portion located at a lower portion of the cell holder and disposed to contact the second electrode terminals; and a rod-shaped second terminal portion extending vertically from the second connection portion through an empty space formed inside the cell holder so that a first end of the rod-shaped second terminal portion is disposed above the cell holder; wherein the cell holder includes unit cell body covers, each unit cell cover having a cylindrical shape so that the plurality of cylindrical battery cells are inserted therein, respectively, wherein the unit cell body covers are arranged in a triangular shape so that circumferential surfaces of neighboring unit cell body covers are attached to each other; wherein the unit cell body covers are provided so that at least three unit cell body covers are integrated, and the empty space is a region surrounded by the at least three unit cell body covers that are in contact with each other.