Disclosed herein is a prismatic battery pack including an electrode assembly of a cathode/separator/anode structure impregnated with an electrolyte, a prismatic container, in which the electrode assembly is mounted, the prismatic container having at least one depressed groove formed at a bottom thereof in a longitudinal direction of the prismatic battery pack, a cap plate coupled to an open upper end of the prismatic container, in which the electrode assembly is mounted, a protection circuit module (PCM) including a protection circuit to control operation of the prismatic battery pack, the PCM being loaded on the cap plate, and an insulative cap mounted to the prismatic container while surrounding the PCM.