In a residual capacity correction method for a battery, a count of one cycle is made each time an accumulated quantity of a charge capacity of a battery reaches a learning capacity of the battery at that time, and the learning capacity is decreased by a specified cycle degradation capacity per charge of the one cycle, alternatively a decreasing rate of the learning capacity is specified as a keeping degradation capacity while a keeping temperature and a residual capacity of the battery are used as parameters, and as a keeping time passes, the learning capacity is decreased by the keeping degradation capacity specified from the keeping temperature and the residual capacity of the battery.