[PROBLEM] To provide a battery pack achieving a thin and compact size. [SOLUTION] A battery pack 100 according to the present invention is formed by stacking a plurality of battery assemblies 100M, 100N that are each provided with at least a pair of the unit cells 110 that are stacked in the thickness direction and that have a cell body 110H, which includes a power generation element 111 and is formed into a flat shape, and an electrode tab 113 protruding out from the cell body, and an insulating spacer 121 is disposed between the electrode tabs of the pair of stacked unit cells. In the present invention, the spacer holds intra-assembly electrode tabs 114 of the pair of unit cells; the pair of held unit cells are electrically connected to each other in the battery assembly; the distal end portions 115a of a pair of intra-assembly electrode tabs that electrically connect the adjacent battery assemblies to each other are bent in the stacking direction of the battery assemblies on a side of a surface among the surfaces of the spacer positioned on the opposite side of the cell body; and the bent portions are electrically connected to each other.