A battery pack includes a plurality of battery modules including a plurality of cells 100 aligned and accommodated in a case, wherein a battery assembly 200 in which the plurality of cells 100 are aligned in a row is used as a unit, and the multiple ones of the battery assembly 200 are aligned in each battery module. The battery modules are a first battery module 300 in which the plurality of battery assemblies 200 are aligned in parallel and second battery modules 400A, 400B in which the plurality of battery assemblies 200 are aligned in series, and the first battery module 300 and the second battery modules 400A, 400B are combined with each other to form the battery pack.