A battery pack comprising: a cell group including a plurality of unit cells stacked in a stacking direction, each of the unit cells including a cell body having a power generation element and a flat shape, and an electrode tab protruding out from the cell body, and the electrode tabs having distal end portions bent along the stacking direction of the unit cells; a spacer disposed between adjacent electrode tabs of a plurality of electrode tabs that are adjacent to each other in the stacking direction, to maintain an interval between the adjacent electrode tabs in the stacking direction; a plurality of flat plate shaped bus bars electrically connecting the electrode tabs of at least two of the unit cells to each other; and a bus bar holder that holds the plurality of flat plate shaped bus bars, characterized in that the bus bar holder comprises a restricting member that: is disposed between distal end portions of the adjacent electrode tabs that are adjacent in the stacking direction, the distal end portions extending along the stacking direction, extends along the stacking direction, and restricts a stacking direction positions of each of the distal end portions of the adjacent electrode tabs by sandwiching the adjacent electrode tabs with the spacer, and the distal end portions of the adjacent electrode tabs are welded to a surface of the plurality of flat plate shaped bus bars facing the unit cells, in a state in which the stacking direction positions of each of the distal end portions of the adjacent electrode tabs is restricted by the restricting member and the spacer. a cell group including a plurality of unit cells stacked in a stacking direction, each of the unit cells including a cell body having a power generation element and a flat shape, and an electrode tab protruding out from the cell body, and the electrode tabs having distal end portions bent along the stacking direction of the unit cells; a spacer disposed between adjacent electrode tabs of a plurality of electrode tabs that are adjacent to each other in the stacking direction, to maintain an interval between the adjacent electrode tabs in the stacking direction; a plurality of flat plate shaped bus bars electrically connecting the electrode tabs of at least two of the unit cells to each other; and a bus bar holder that holds the plurality of flat plate shaped bus bars, characterized in that the bus bar holder comprises a restricting member that: is disposed between distal end portions of the adjacent electrode tabs that are adjacent in the stacking direction, the distal end portions extending along the stacking direction, extends along the stacking direction, and restricts a stacking direction positions of each of the distal end portions of the adjacent electrode tabs by sandwiching the adjacent electrode tabs with the spacer, and is disposed between distal end portions of the adjacent electrode tabs that are adjacent in the stacking direction, the distal end portions extending along the stacking direction, extends along the stacking direction, and restricts a stacking direction positions of each of the distal end portions of the adjacent electrode tabs by sandwiching the adjacent electrode tabs with the spacer, and the distal end portions of the adjacent electrode tabs are welded to a surface of the plurality of flat plate shaped bus bars facing the unit cells, in a state in which the stacking direction positions of each of the distal end portions of the adjacent electrode tabs is restricted by the restricting member and the spacer.