Abstract: A thermal conductive mechanism for a battery pack made up of a stack of a plurality of sub-battery modules each of which includes a plurality of battery cells arrayed thereon. The sub-battery modules each has opposed major surfaces and are laid to overlap each other in a direction perpendicular to the major surfaces. The thermal conductive mechanism is equipped with plates provided one for each of the sub-battery modules. Each of the plates has a given number of the battery cells disposed thereon and also has heat transfer surfaces extending in a planar direction of the plate. The heat transfer surfaces are placed in one of direct and indirect contact with the given number of the battery cells to achieve transfer of heat therebetween, thereby equalizing the temperature in each of the battery cells and also minimizing a difference in temperature among the battery cells.