A battery pack, comprising: - a number, m, of battery cells arranged in a first direction, wherein each of the battery cells includes: a terminal surface including at least one electrode terminal thereon, a bottom surface opposite to the terminal surface in a third direction that perpendicularly intersects with the first direction, a pair of large surfaces at opposite sides of the battery cells in the first direction that connect the terminal surface to the bottom surface, each large surface having a first area, and a pair of lateral surfaces at opposite sides of the battery cells in a second direction that perpendicularly intersects with the first direction and the third direction and that connect the terminal surface to the bottom surface, each lateral surface having a second area, the second area being smaller than the first area, - a plurality of spacer units, wherein each of the spacer units extends across a number, n, of the battery cells, in which n < m, each spacer unit including << - >> in the first direction and connecting the plurality of spacing bars to each other; << a plurality of spacing bars extending in the third direction and disposed between the large surfaces of adjacent battery cells; and connection bars extending >> wherein a plurality of spacer units arranged in the first direction form a spacer, and wherein spacers facing each other in the second direction form a pair of spacers, the spacers of a pair of spacers being fixed to the lateral surfaces on opposite sides of the battery cells, such that the spacing bars belonging to a pair of spacers form pairs of spacing bars facing each other in the second direction. - a number, m, of battery cells arranged in a first direction, wherein each of the battery cells includes: a terminal surface including at least one electrode terminal thereon, a bottom surface opposite to the terminal surface in a third direction that perpendicularly intersects with the first direction, a pair of large surfaces at opposite sides of the battery cells in the first direction that connect the terminal surface to the bottom surface, each large surface having a first area, and a pair of lateral surfaces at opposite sides of the battery cells in a second direction that perpendicularly intersects with the first direction and the third direction and that connect the terminal surface to the bottom surface, each lateral surface having a second area, the second area being smaller than the first area, a terminal surface including at least one electrode terminal thereon, a bottom surface opposite to the terminal surface in a third direction that perpendicularly intersects with the first direction, a pair of large surfaces at opposite sides of the battery cells in the first direction that connect the terminal surface to the bottom surface, each large surface having a first area, and a pair of lateral surfaces at opposite sides of the battery cells in a second direction that perpendicularly intersects with the first direction and the third direction and that connect the terminal surface to the bottom surface, each lateral surface having a second area, the second area being smaller than the first area, - a plurality of spacer units, wherein each of the spacer units extends across a number, n, of the battery cells, in which n < m, each spacer unit including << - >> in the first direction and connecting the plurality of spacing bars to each other; << a plurality of spacing bars extending in the third direction and disposed between the large surfaces of adjacent battery cells; and connection bars extending >> wherein a plurality of spacer units arranged in the first direction form a spacer, and wherein spacers facing each other in the second direction form a pair of spacers, the spacers of a pair of spacers being fixed to the lateral surfaces on opposite sides of the battery cells, such that the spacing bars belonging to a pair of spacers form pairs of spacing bars facing each other in the second direction. << a plurality of spacing bars extending in the third direction and disposed between the large surfaces of adjacent battery cells; and connection bars extending >> wherein a plurality of spacer units arranged in the first direction form a spacer, and wherein spacers facing each other in the second direction form a pair of spacers, the spacers of a pair of spacers being fixed to the lateral surfaces on opposite sides of the battery cells, such that the spacing bars belonging to a pair of spacers form pairs of spacing bars facing each other in the second direction.