An apparatus for diagnosing an abnormality in a cell balancing circuit in a battery pack including a plurality of cells corresponding to each cell balancing circuit, the apparatus comprising: a cell balancing circuit connected in parallel to a voltage sensing line (L0-L6) connected to both terminals of each cell, and including a cell balancing switch and a discharge resistor (Rb); a diagnosis resistor (Rc) installed on the voltage sensing line at the side of the cell with respect to a node (n0-n6) (a high potential node and a low potential node) at which the cell balancing circuit and the cell voltage sensing line are connected; a voltage sensing circuit configured to output a voltage corresponding to a voltage difference between the high potential node and the low potential node (hereinafter referred to as an 'inter-node voltage value'); and. a control unit configured to: store inter-node voltage values (hereinafter referred to as a 'cell voltage values') obtained in a situation where the cell balancing switches are in a turn-off state, store inter-node voltage values (hereinafter referred to as a 'diagnosis voltage values'), each inter-node voltage values being obtained by turning on a cell balancing switch of a cell balancing circuit to be diagnosed among the cell balancing circuits from a situation where the cell balancing switches included in the cell balancing circuit to be diagnosed and in the cell balancing circuits adjacent to the cell balancing circuit to be diagnosed are in a turn-off state, characterized in that the control unit is further configured to: calculate a difference value between adjacent cell voltage values (hereinafter referred to as a 'cell difference value') and a difference value between adjacent diagnosis voltage values (hereinafter referred to as a 'diagnosis difference value'), and determine whether an abnormality is present in the cell balancing circuit by analyzing a change pattern of a difference value between the cell difference value and the diagnosis difference value (hereinafter referred to as a 'determination value'). a cell balancing circuit connected in parallel to a voltage sensing line (L0-L6) connected to both terminals of each cell, and including a cell balancing switch and a discharge resistor (Rb); a diagnosis resistor (Rc) installed on the voltage sensing line at the side of the cell with respect to a node (n0-n6) (a high potential node and a low potential node) at which the cell balancing circuit and the cell voltage sensing line are connected; a voltage sensing circuit configured to output a voltage corresponding to a voltage difference between the high potential node and the low potential node (hereinafter referred to as an 'inter-node voltage value'); and. a control unit configured to: store inter-node voltage values (hereinafter referred to as a 'cell voltage values') obtained in a situation where the cell balancing switches are in a turn-off state, store inter-node voltage values (hereinafter referred to as a 'diagnosis voltage values'), each inter-node voltage values being obtained by turning on a cell balancing switch of a cell balancing circuit to be diagnosed among the cell balancing circuits from a situation where the cell balancing switches included in the cell balancing circuit to be diagnosed and in the cell balancing circuits adjacent to the cell balancing circuit to be diagnosed are in a turn-off state, characterized in that the control unit is further configured to: calculate a difference value between adjacent cell voltage values (hereinafter referred to as a 'cell difference value') and a difference value between adjacent diagnosis voltage values (hereinafter referred to as a 'diagnosis difference value'), and determine whether an abnormality is present in the cell balancing circuit by analyzing a change pattern of a difference value between the cell difference value and the diagnosis difference value (hereinafter referred to as a 'determination value'). store inter-node voltage values (hereinafter referred to as a 'cell voltage values') obtained in a situation where the cell balancing switches are in a turn-off state, store inter-node voltage values (hereinafter referred to as a 'diagnosis voltage values'), each inter-node voltage values being obtained by turning on a cell balancing switch of a cell balancing circuit to be diagnosed among the cell balancing circuits from a situation where the cell balancing switches included in the cell balancing circuit to be diagnosed and in the cell balancing circuits adjacent to the cell balancing circuit to be diagnosed are in a turn-off state, characterized in that the control unit is further configured to: calculate a difference value between adjacent cell voltage values (hereinafter referred to as a 'cell difference value') and a difference value between adjacent diagnosis voltage values (hereinafter referred to as a 'diagnosis difference value'), and determine whether an abnormality is present in the cell balancing circuit by analyzing a change pattern of a difference value between the cell difference value and the diagnosis difference value (hereinafter referred to as a 'determination value'). calculate a difference value between adjacent cell voltage values (hereinafter referred to as a 'cell difference value') and a difference value between adjacent diagnosis voltage values (hereinafter referred to as a 'diagnosis difference value'), and determine whether an abnormality is present in the cell balancing circuit by analyzing a change pattern of a difference value between the cell difference value and the diagnosis difference value (hereinafter referred to as a 'determination value').