An apparatus protects a battery by comparison of full charge capacity. The apparatus includes a fuse connected on a circuit path along which a charging or discharging current flows, a fuse control switch for selectively opening or closing an operating current applied to the fuse, and a controller for calculating an actual value and a reference value of a full charge capacity of a battery, comparing the actual value with the reference value, and then controlling the fuse control switch according to the comparison result to melt and cut the fuse. Thus, an abnormal state of a battery may be found and controlled at an early stage, so it is possible to prevent any problem such as firing and thus improve the safety of a battery.