A Battery Management System (BMS) semiconductor device having a leakage current detection function, may include: a comparator configured to compare a voltage of a balancing terminal connected to a positive voltage terminal of a battery cell and a voltage of a lower sensing terminal connected to a negative voltage terminal of the battery cell and output a result of the comparing; an ADC connected to the upper sensing terminal and the lower sensing terminal and configured to sense a voltage difference between the upper sensing terminal connected to the positive voltage terminal of the battery cell and the lower sensing terminal; and a leakage current determining unit connected to the ADC and the comparator and configured to set a variable threshold value according to the difference value sensed by the ADC and determine whether a leakage current is generated by using the result of the comparing in the comparator and the variable threshold value.