ProblemTo maintain high fuel consumption performance also in the charging by a drive of an alternator at the non-deceleration in a power source management system that drives the alternator during vehicle deceleration to charge a battery.SolutionA power generation cost of an alternator is found from a rotational speed and torque of an engine at the non-deceleration The alternator is driven only when an SOC of a battery is in a drive permission zone Z in which, based upon the power generation cost, the SOC and the power consumption, the SOC is the lower as the power generation cost is the higher and the SOC is the higher as the power consumption is the higher. The fuel consumption performance is higher as compared to a conventional example of always driving the alternator when the SOC is equal to or less than a maximum upper limit value SOCm regardless of the power generation cost as an index of an engine efficiency.