An overcharge preventing device comprising: an input voltage dividing unit configured to be connected across at least one battery cell in a battery pack including a plurality of battery cells, for dividing a voltage of the battery cell, and including a plurality of resistors connected to each other in series; a voltage sensing unit configured of a shunt regulator, a reference of the shunt regulator connected between the resistors of the input voltage dividing unit, a cathode of the shunt regulator connected to a positive electrode of the battery cell to which the input voltage dividing unit is connected through a coil unit of a power cut-off unit, an anode of the shunt regulator connected to a negative electrode of the battery cell to which the input voltage dividing unit is connected, the power cut-off unit including the coil unit and a switch unit, one side of the coil unit connected to the positive electrode of the battery cell to which the input voltage dividing unit is connected and the other side thereof is connected to the cathode of the shunt regulator, and one side of the switch unit connected to a line connectable to a relay coil side controlled and the other side thereof is connected to a common line (-), wherein the input voltage dividing unit is configured to electrically conduct the anode and the cathode when an input voltage of the reference of the shunt regulator is input as a predetermined voltage or more, wherein the power cut-off unit is configured of a non-return circuit configured for operating the switch unit when the power is applied to the coil unit by the operation of the voltage sensing unit, and wherein the power cut-off unit is configured to cut off an electrical power of the relay coil regardless of the control of a battery management system to cut off electrical power of the battery pack when the battery cell is overcharged, and even if the overcharge state of the battery cell is released, the power cut-off unit is configured to not return to an initial state while continuously maintaining the internal switch in current state in order to prevent an ignition or an explosion of the battery cell until a separate control is performed. an input voltage dividing unit configured to be connected across at least one battery cell in a battery pack including a plurality of battery cells, for dividing a voltage of the battery cell, and including a plurality of resistors connected to each other in series; a voltage sensing unit configured of a shunt regulator, a reference of the shunt regulator connected between the resistors of the input voltage dividing unit, a cathode of the shunt regulator connected to a positive electrode of the battery cell to which the input voltage dividing unit is connected through a coil unit of a power cut-off unit, an anode of the shunt regulator connected to a negative electrode of the battery cell to which the input voltage dividing unit is connected, the power cut-off unit including the coil unit and a switch unit, one side of the coil unit connected to the positive electrode of the battery cell to which the input voltage dividing unit is connected and the other side thereof is connected to the cathode of the shunt regulator, and one side of the switch unit connected to a line connectable to a relay coil side controlled and the other side thereof is connected to a common line (-), wherein the input voltage dividing unit is configured to electrically conduct the anode and the cathode when an input voltage of the reference of the shunt regulator is input as a predetermined voltage or more, wherein the power cut-off unit is configured of a non-return circuit configured for operating the switch unit when the power is applied to the coil unit by the operation of the voltage sensing unit, and wherein the power cut-off unit is configured to cut off an electrical power of the relay coil regardless of the control of a battery management system to cut off electrical power of the battery pack when the battery cell is overcharged, and even if the overcharge state of the battery cell is released, the power cut-off unit is configured to not return to an initial state while continuously maintaining the internal switch in current state in order to prevent an ignition or an explosion of the battery cell until a separate control is performed.