An eco-friendly power source, such as a battery module for a transportation vehicle includes a plurality of battery cells each including an electrode assembly and an electrode tab protruding from the electrode assembly, and a bus bar assembly coupled to the electrode tabs and connecting the plurality of battery cells. The bus bar assembly includes a main frame having a slit into which the electrode tab is inserted, a bus bar positioned on an outer surface of the main frame and electrically connected to the electrode tab, a plurality of inner frames facing an inner surface of the main frame and spaced apart from each other in a direction in which the battery cells are stacked, and a venting induction portion formed in a concave shape toward the electrode assembly and formed at an upper end portion of at least one of the plurality of inner frames.