A battery charging apparatus enables a mobile phone to be used not only for its own use but also as a cordless telephone. The battery charging apparatus includes a telephone section and a Bluetooth section. The telephone section is connected between a public network and the Bluetooth section so as to interface an incoming call from the public network to the combined cordless/mobile phone through the Bluetooth section and to interface a call oriented from the combined cordless/mobile phone to the public network through the Bluetooth section. The Bluetooth section is connected between the telephone section and the combined cordless/mobile phone so as to transmit and receive wireless data.