A wireless power transmitter for charging a wireless power receiver is provided. The wireless power transmitter includes a power transmission unit configured to transmit power for charging the wireless power receiver, by using a current applied to the power transmission unit, a communication module configured to receive out-of-band communication signal from the wireless power receiver and a controller configured to apply the current to the power transmission unit to transmit power in response to receiving the out-of-band communication signal from the wireless power receiver.