A battery pack comprising: a battery module array having battery modules which are arranged in a lateral direction in two or more rows, each of the battery modules being configured to have a structure in which battery cells or unit modules, each of which has two or more battery cells mounted therein, are stacked in a state in which the battery cells or the unit modules are erected vertically; a base plate on which the battery modules are stacked in a vertically erected state; a pair of main members provided at a front and rear of the battery module array to support load of the battery modules, opposite ends of each of the main members being fastened to an external device; a pair of end plates disposed in tight contact with the front and rear of the battery module array in a state in which a lower end of each of the end plates is fixed to the base plate; and supporting bars connected between upper parts or side parts of the end plates so as to interconnect and support the end plates, wherein each of the end plates is formed in the shape of a single body having a size of the front or rear corresponding to the battery module array to minimize deformation of the battery pack when the battery pack is vibrated in an up and down direction, wherein each of the end plates comprises a body part disposed in contact with the battery module array, an upper end wall, a lower end wall, and a pair of side walls, the upper end wall, the lower end wall, and the side walls protruding outward from a perimeter of the body part; wherein the upper end wall of each of the end plates protrudes upward from a top of the battery module array so that the supporting bars can be easily mounted to the end plates, and wherein the upwardly protruding height is equivalent to 2 to 20% of a height of the battery module array. a battery module array having battery modules which are arranged in a lateral direction in two or more rows, each of the battery modules being configured to have a structure in which battery cells or unit modules, each of which has two or more battery cells mounted therein, are stacked in a state in which the battery cells or the unit modules are erected vertically; a base plate on which the battery modules are stacked in a vertically erected state; a pair of main members provided at a front and rear of the battery module array to support load of the battery modules, opposite ends of each of the main members being fastened to an external device; a pair of end plates disposed in tight contact with the front and rear of the battery module array in a state in which a lower end of each of the end plates is fixed to the base plate; and supporting bars connected between upper parts or side parts of the end plates so as to interconnect and support the end plates, wherein each of the end plates is formed in the shape of a single body having a size of the front or rear corresponding to the battery module array to minimize deformation of the battery pack when the battery pack is vibrated in an up and down direction, wherein each of the end plates comprises a body part disposed in contact with the battery module array, an upper end wall, a lower end wall, and a pair of side walls, the upper end wall, the lower end wall, and the side walls protruding outward from a perimeter of the body part; wherein the upper end wall of each of the end plates protrudes upward from a top of the battery module array so that the supporting bars can be easily mounted to the end plates, and wherein the upwardly protruding height is equivalent to 2 to 20% of a height of the battery module array.