A method of controlling a wireless power transmitter is discussed. The method includes transmitting a power signal having a predetermined strength; measuring a quality factor and a peak frequency of a coil of the wireless power transmitter using the power signal; receiving reference values including a reference quality factor and a reference peak frequency of a wireless power receiver; determining whether or not a foreign object is present in a charging area of the wireless power transmitter based on a comparison of the reference quality factor with the measured quality factor and a comparison of the reference peak frequency with the measured peak frequency; transmitting response signals indicating a result of the determination; and determining whether to continue or stop a wireless charging procedure based on the response signals.