This study examines the efficiency in operating performances of domestic branches of a well‐known Taiwanese Bank by adopting a data envelopment analysis (DEA). The empirical findings show that most branches are gauged inefficiently. Some should strengthen professional training of managers to improve the pure technical efficiency; others should enhance the scale efficiency. In addition, based on the empirical results, strategies to improve the efficiency of human resources by allocating workforce are proposed. Appropriately adjusting the number of staffs among branches is an effective way to increase the operating performances of the bank.