A battery management apparatus for a vehicle includes a battery, an alternator, a battery detection unit, a battery controller generating an initial state of charge by using initial state information of the battery at startup, generating an internal resistance of the battery using a voltage value and a current value of the battery, generating a first state of charge by using a driving state information of the battery, a battery charging efficiency, and the initial state of charge when the startup is off, generating a second state of charge by using the off state information of the battery when the off time after the start-off is greater than or equal to the reference time, and resetting the battery charging efficiency based on the first and second state of charge, and a vehicle controller for receiving the battery charging efficiency from the battery controller, and controlling the alternator based thereon to charge the battery.