Disclosed herein is a battery pack case in which a battery module (32) having a plurality of stacked unit cells (30) is mounted. The battery pack case is provided at an upper part and a lower part thereof with a coolant inlet port (10′) and a coolant outlet port (20′), respectively. The coolant inlet port (10′) and the coolant outlet port (20′) are directed in opposite directions. The battery pack case is further provided with a coolant introduction part (40′) and a coolant discharge part. An upper end inside part of the coolant introduction part (40′) is configured in a structure in which an incline plane starting from an end opposite to the coolant inlet port (10′) has an inclination increasing toward the coolant inlet port (10′) with respect to the top of the cell stack.