Battery Cell Diagnostic Device and Method

A device and method for diagnosing an increase in resistance of a lead unit of a battery cell, including a first voltage measurement step in which when a battery pack is in an open circuit voltage state, a voltage is measured for each unit cell of the battery pack, a second voltage measurement step in which, when the battery pack is in a charging or discharging state, a voltage is measured for each unit cell according to a predetermined current flowing through the battery pack, and a step for comparing, for each unit cell, a voltage measured in the first voltage measurement step and a voltage measured in the second voltage measurement step, and detecting whether the unit cell is abnormal.