BATTERY MODULE

A battery module according to the present disclosure comprises a cell stack comprising a plurality of battery cells; and a module case covering the outside of the cell stack. A module case comprises a first case comprising a rib and a first coupling portion that has a greater thickness than that of the rib and that is connected to a side of the rib; a second case comprising a second coupling portion facing an upper portion of the rib and a side of the first coupling portion; a tunnel portion formed between the rib, the first coupling portion, and the second coupling portion; and a welding portion in which a boundary area of the first coupling portion and the second coupling portion is welded.