A battery pack, comprising: a plurality of battery modules (200, 201,..., 213) arranged in a front and rear direction, wherein each of the plurality of battery modules includes: a plurality of cylindrical battery cells arranged in a horizontal direction and having electrode terminals formed at an upper portion and a lower portion thereof, respectively; a module housing having a plurality of hollows in which the plurality of cylindrical battery cells are inserted and accommodated; and a connection plate (220, 221, 222) having a body portion located at the upper portion or the lower portion of the plurality of cylindrical battery cells and provided with a plurality of connection terminals respectively in electrical contact and connection with the electrode terminal (111a,111b) formed at one of the plurality of cylindrical battery cells, and a connection portion configured to protrusively extend in a left direction or a right direction from the body portion so that a protrusively extending portion of the connection portion is bent upward or downward from the body portion and a bent end of the connection portion is in contact and connection with a portion of another connection plate. a plurality of battery modules (200, 201,..., 213) arranged in a front and rear direction, wherein each of the plurality of battery modules includes: a plurality of cylindrical battery cells arranged in a horizontal direction and having electrode terminals formed at an upper portion and a lower portion thereof, respectively; a module housing having a plurality of hollows in which the plurality of cylindrical battery cells are inserted and accommodated; and a connection plate (220, 221, 222) having a body portion located at the upper portion or the lower portion of the plurality of cylindrical battery cells and provided with a plurality of connection terminals respectively in electrical contact and connection with the electrode terminal (111a,111b) formed at one of the plurality of cylindrical battery cells, and a connection portion configured to protrusively extend in a left direction or a right direction from the body portion so that a protrusively extending portion of the connection portion is bent upward or downward from the body portion and a bent end of the connection portion is in contact and connection with a portion of another connection plate. a plurality of cylindrical battery cells arranged in a horizontal direction and having electrode terminals formed at an upper portion and a lower portion thereof, respectively; a module housing having a plurality of hollows in which the plurality of cylindrical battery cells are inserted and accommodated; and a connection plate (220, 221, 222) having a body portion located at the upper portion or the lower portion of the plurality of cylindrical battery cells and provided with a plurality of connection terminals respectively in electrical contact and connection with the electrode terminal (111a,111b) formed at one of the plurality of cylindrical battery cells, and a connection portion configured to protrusively extend in a left direction or a right direction from the body portion so that a protrusively extending portion of the connection portion is bent upward or downward from the body portion and a bent end of the connection portion is in contact and connection with a portion of another connection plate.