A battery module includes a plurality of unit batteries, each of which
includes an electrode assembly having positive and negative electrodes
and a separator interposed therebetween, a casing which has an opened top
face and stores the electrode assembly, and a cap assembly disposed on
top of the casing. The battery module has an interconnection member which
interconnects first and second unit batteries out of a plurality of the
unit batteries by connecting a lower portion of the first unit battery
with an upper portion of the second unit battery. Peripheral portions of
the interconnection member are engaged with a recessed portion formed by
making a step in the casing of the first unit battery.