A cell balance control unit is provided, including: a discharge circuit connected to each of a plurality of battery cells constituting a battery in parallel; a voltage detecting circuit that detects a voltage of each of the battery cells; and a control device that controls each of the switching elements of the discharge circuit so that the voltage of each of the battery cells is made uniform based on voltage detection results of each of the battery cells, wherein the control device controls the switching elements of the discharge circuits connected to the adjacent battery cells in each different duty ratio, and detects disconnection of wirings extracted from both ends of each battery cell based on a potential difference between the adjacent battery cells.