A method for detecting a foreign object disposed in a charging area of a wireless power transmitter can include transmitting, by the wireless power transmitter, a power signal having a predetermined strength; measuring, via a controller, a peak frequency of the power signal; receiving, from a wireless power receiver, information about a reference peak frequency of the wireless power receiver; determining, via the controller, a threshold frequency based on the reference peak frequency; and determining, via the controller, whether the foreign object is present in the charging area based on a comparison of the measured peak frequency of the power signal with the determined threshold frequency.