The present invention provides a battery module which includes: a battery stack formed by stacking a plurality of battery cells on each other, each of which includes electrode tabs; a first case unit including a bottom section which surrounds one side of the battery stack and a pair of first sidewalls located on both sides of the battery stack in a direction in which battery cells are stacked; and a second case unit including a top section which surrounds the other side of the battery stack and a pair of second sidewalls located on both sides of the battery stack in the direction in which battery cells are stacked, wherein the first sidewall and the second sidewall are located on both sides of the battery stack in the direction in which battery cells are stacked, in a state in which at least portions thereof are overlapped with each other.