Provided is a battery pack. The battery pack includes a sub-holder assembly including first and second sub-holders arranged adjacent to each other, each saccommodating a plurality of battery cells and including side portions extending in first and second directions different from each other, a first inner plate and a first outer plate provided at an inner position and an outer position of the sub-holder assembly, respectively, and extending in the first direction with the first sub-holder therebetween, the first inner plate and the first outer plate including an upper locking protrusion and a lower locking protrusion that protrude toward an upper surface and a lower surface of the first sub-holder, respectively, in a third direction intersecting with the first and second directions and a nut member that is arranged together with the lower locking protrusion in the first direction, and a fastening member sequentially passing through a cooling plate and the nut member and accommodated in a lower portion of the first sub-holder, wherein the cooling plate is disposed below the first and second sub-holders.