An in-vehicle battery pack includes: battery stacks in which a plurality of battery cells is stacked with a spacer member interposed between the battery cells; a casing in which the battery stacks are housed in two stages in a vertical direction; and an intervening member that is provided between the battery stacks and bottom portions so as to be interposed between a protruding portion protruding to the bottom surface of the battery stack and a wall of the casing.