A disconnection detection device comprising: CR filters provided for each respective battery cell (B1, B2) of a battery pack in which the battery cells are connected in series; discharge circuits each connected between a battery cell (B1, B2) and the CR filter , and configured to discharge the battery cell (B1, B2) when cell voltages of the battery cells (B1, B2) are made balanced; and a detection unit configured to: alternately and successively discharge two of the battery cells (B1, B2) connected in series that are adjacent to each other, after a predetermined time has passed from finish of discharge of each of the battery cells (B1, B2), detect a voltage of a first detection line (L1) wherein the first detection line is configured to detect a voltage at a point between a positive electrode of one of the adjacent battery cells (B1, B2) and a negative electrode of another of the adjacent battery cells (B1, B2), and detect a voltage of a second detection line (L2) wherein the second detection line is configured to detect a voltage of a negative electrode of the one of the adjacent battery cells (B1, B2); and detect disconnection of the first detection line (L1) based on a difference between the two detected voltages. CR filters provided for each respective battery cell (B1, B2) of a battery pack in which the battery cells are connected in series; discharge circuits each connected between a battery cell (B1, B2) and the CR filter , and configured to discharge the battery cell (B1, B2) when cell voltages of the battery cells (B1, B2) are made balanced; and a detection unit configured to: alternately and successively discharge two of the battery cells (B1, B2) connected in series that are adjacent to each other, after a predetermined time has passed from finish of discharge of each of the battery cells (B1, B2), detect a voltage of a first detection line (L1) wherein the first detection line is configured to detect a voltage at a point between a positive electrode of one of the adjacent battery cells (B1, B2) and a negative electrode of another of the adjacent battery cells (B1, B2), and detect a voltage of a second detection line (L2) wherein the second detection line is configured to detect a voltage of a negative electrode of the one of the adjacent battery cells (B1, B2); and detect disconnection of the first detection line (L1) based on a difference between the two detected voltages. alternately and successively discharge two of the battery cells (B1, B2) connected in series that are adjacent to each other, after a predetermined time has passed from finish of discharge of each of the battery cells (B1, B2), detect a voltage of a first detection line (L1) wherein the first detection line is configured to detect a voltage at a point between a positive electrode of one of the adjacent battery cells (B1, B2) and a negative electrode of another of the adjacent battery cells (B1, B2), and detect a voltage of a second detection line (L2) wherein the second detection line is configured to detect a voltage of a negative electrode of the one of the adjacent battery cells (B1, B2); and detect disconnection of the first detection line (L1) based on a difference between the two detected voltages. <EOS>