To provide a charging device and method, capable of inexpensively and fully charging a battery, without especially using an expensive component and a special circuit.

The charging device includes an AC input power supply, the battery, a master charger and one or a plurality of slave chargers. The master charger calculates total output current from its own-master output current and slave output current of the slave charger, and determines the own-output current by comparing the total output current with target output current determined by a characteristic of the battery. The slave charger determines its own-slave output current by comparing target input current determined by master input current of the master charger with the own slave-input current.