Disclosed are a system for and a method of determining the cause of a defect of a battery, which is specifically attributable to a human error, through electrochemical impedance spectroscopy (EIS). The system includes an impedance measurement unit for measuring an impedance value of a battery while sequentially applying AC current signals of respective frequencies to the battery, a controller for determining the cause of the defect of the battery on the basis of the measured impedance value, and a table in which each of impedance value ranges is associated with a cause of a defect. The controller determines a cause of a defect of the battery by comparing the measured impedance value and each of the impedance value ranges.