Disclosed is a battery pack configured to have a structure in which two or more battery modules, each including a plurality of battery cells or unit modules (unit cells) which can be charged and discharged, are mounted in a space defined between a pack case and a base plate, wherein cooling members, each including a heat dissipation fin disposed in contact with outsides of corresponding ones of the unit cells and a coolant conduit connected to a lower end of the heat dissipation fin to allow a coolant to flow therealong, are mounted at interfaces between the unit cells, the base plate, located below the battery modules, is configured to form a coolant flow channel having a coolant flow direction corresponding to the coolant flow direction in the coolant conduit, the pack case is coupled to the base plate in a state in which the battery modules are mounted on the base plate.