NOVELTY - The case has square type battery cells (110) inserted into inclinedly formed insertion parts of a cooling case (120). Cooling passages are provided in the cooling case and inclinedly formed so as to move a cooling medium i.e. cooling water, between the battery cells. A refrigerant inlet (123) is formed at a side of the cooling passage to be introduced with the cooling medium. A refrigerant outlet (124) is formed at another side of the cooling passage to discharge the cooling medium passing through the battery cells. The refrigerant inlet is formed above the refrigerant outlet.    USE - Battery pack case i.e. secondary battery pack case, for portable electronic devices such as a mobile phone, a notebook computer, a digital camera and an MPEG-1 media layer-3(MP3) player, and vehicle such as an electric vehicle, hybrid electric vehicle, gasoline vehicle, diesel vehicle and car.    ADVANTAGE - The cooling medium naturally flows through the refrigerant inlet and the refrigerant outlet formed at different heights and the cooling passages inclinedly formed and connecting the refrigerant inlet with the refrigerant outlet so as to avoid usage of separate power source to move the cooling medium, thus reducing additional power consumption for moving the cooling medium, and hence reducing production and maintenance costs. The battery cell is inserted between the fixing parts to fix the sides of the battery cell and prevent the battery cell from moving, and is inserted into a space in which air can flow through sides of the battery cell, thus more efficiently cooling the battery cell. The case can increase cooling efficiency of the battery cell and increase service life of the battery cell by contacting the cooling passage to a front surface of the battery cell by uniformly supplying the amount of cooling medium to the battery cell. The case can increase cooling efficiency by dissipating heat from the front surfaces of the battery cell so as to uniformly apply amount of a cooling medium supplied to the battery cell.    DETAILED DESCRIPTION - The cooling case is made of aluminum, copper, iron, stainless steel, ceramic, and polymer materials.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a battery pack case.    Square type battery cells (110)    Anode and cathode terminals (111)    Cooling case (120)    Refrigerant inlets (123, 123a)    Refrigerant outlets (124, 124a)