A battery pack includes a casing, a cell group, a bracket, cell connection pieces, and output terminals. A plane where the output terminals of the battery pack are located is defined as an upper plane, a plane where the output terminals of the cell group are located is defined as a front plane, and a plane perpendicular to the upper plane and the front plane is defined as a side plane. One of the cell connection pieces includes a bracket-fixed surface, a cell connection surface, and a power supply output surface. The bracket-fixed surface is fixed on the bracket and parallel to the side plane. The cell connection surface is connected to the power supply output terminals of the cell group and parallel to the front plane. The power supply output surface is connected to the output terminals and parallel to the upper plane.