To obtain an apparatus and a method, in which a full charging stage can be detected with good accuracy, irrespective of an ambient temperature or the magni tude of a discharge capacity, immediately before the charging operation of a battery, and in which it is possible to surely prevent the battery from being charging excessive ly.

When the temperature of a battery detected by a temperature sensor is at a prescribed value or lower, a temperature control part controls a charger by a charging control part, and a constant-current charging operation is performed on the battery. At this time, the temperature control part records the minimum temperature of the battery into a built-in memory. After that, it monitors a rise in the temperature of the battery, it decides the full charging of the battery at a point of time when the temperature of the battery exceeds an additional value of the minimum temperature and a temperature reference value (10°C), and it outputs a charging stop signal to the charging control part, so as to stop the charging operation of the battery. Since the detection of the full charging by the temperature rise of the battery does not depend on the magnitude of the ambient temperature or a discharge capacity immediately before the charging operation of the battery, a full charging state can be detected with good accuracy, and the battery can be prevented surely from being overcharged.