A control device of a secondary battery has a current detection unit (103) that detects a charge current to the secondary battery (101) and a discharge current from the secondary battery (101); a calculation unit (107) that calculates, from the charge current and the discharge current, a charge-discharge efficiency and a discharge-charge efficiency when performing a charge operation and a discharge operation; a deterioration judgment unit (107) that judges a deterioration state of the secondary battery (101) from a temporal change rate of the charge-discharge efficiency and a temporal change rate of the discharge-charge efficiency; and a control unit (107) that sets a charge termination voltage of the secondary battery (101) in accordance with the deterioration state.