A wireless power transmitter includes a power conversion unit configured to transfer wireless power to a wireless power receiver by forming magnetic coupling with the wireless power receiver; and a communication/control unit configured to communicate with the wireless power receiver to control transmission of the wireless power and to perform transmission or reception of data, wherein the communication/control unit further configured to set a target power level based on an operation condition, receive, from the wireless power receiver, a received power packet (RPP) which informs a value of the wireless power received by the wireless power receiver, transmit a bit pattern to the wireless power receiver in response to the RPP, the bit pattern requesting communication initiated by the wireless power transmitter, and receive, from the wireless power receiver, a response packet to allow the communication initiated by the wireless power transmitter.