Provided is a prismatic battery pack, which includes: an electrode assembly having a positive electrode/separation membrane/negative electrode structure impregnated with an electrolyte; a prismatic can, which is a battery case into which the electrode assembly is built, and which has at least one indentation-type groove formed on the bottom surface thereof in the longitudinal direction of the battery pack; a cap plate coupled to the open upper end of the prismatic can into which the electrode assembly is built; a protective circuit module (PCM), which includes a protective circuit that controls the operation of the battery pack, and which is mounted on the cap plate; and an insulation cap which surrounds the PCM and which is coupled to the prismatic can.