A plurality of battery cells (100) are connected in series to each other. A temperature measurement unit (300) measures temperatures of two or more battery cells (100). A battery control unit (400) controls charge and discharge of the battery cells (100) on the basis of the temperatures measured by the temperature measurement unit (300). In addition, when the charge of the battery cells (100) is performed or the discharge of the battery cells (100) is performed, the battery control unit (400) specifies a lowest temperature cell having the lowest temperature and a highest temperature cell having the highest temperature, on the basis of the temperatures measured by the temperature measurement unit (300). In addition, the battery control unit (400) continues the charge or discharge, as it is, when a first condition in which a temperature difference ΔT between the highest temperature cell and the lowest temperature cell is equal to or greater than a reference value T1 is not satisfied. On the other hand, when the temperature difference ΔT satisfies the first condition, the battery control unit (400) outputs a first signal.