Disclosed herein is a pack case for battery packs in which a battery cell array including two or more battery cells arranged in a lateral direction and a protection circuit module (PCM) including a protection circuit to control an operation of the battery pack are mounted, the pack case including a lower case, on which the battery cell array and the protection circuit module are mounted, and an upper case disposed above the lower case so that the upper case covers the lower case to fix the battery cell array and the protection circuit module in place, wherein a lower case is partitioned into a battery cell mounting part, on which the battery cells are mounted, and a protection circuit module mounting part, on which the protection circuit module is mounted, a partition wall is formed at an interface between the battery cell mounting part and the protection circuit module mounting part, and openings, through which electrode terminals of the battery cells are exposed toward the protection circuit module, are formed at portions of the partition wall corresponding to electrical connection regions between the electrode terminals of the battery cells and the protection circuit module.