Disclosed is a method for wirelessly transmitting, by a power transmitter including a primary coil, power. The method may include detecting the placement of objects on a surface of an interface included in the power transmitter and selecting a power receiver which belongs to the detected objects and to which power is to be transmitted, performing digital ping for applying a power signal for detecting and identifying the power receiver to the power receiver and receiving a response to the digital ping from the power receiver, obtaining information about the configuration of the power receiver and establishing a power transfer contract with the power receiver using the configuration information, and wirelessly transmitting the power to the power receiver based on the established power transfer contract.