The present disclosure relates to a foreign object detection method of a wireless power transmitter, and the method may include acquiring the frequency characteristics of a current flowing through a coil within the wireless power transmitter, comparing a peak frequency with a resonant frequency, and detecting whether or not the foreign object is placed on the transmitter through the comparison. In addition, the present disclosure relates to an interference avoidance method of a wireless power transmitter, and the method may include connecting a head unit of an automobile in a wireless manner through a communication device, receiving a first signal for avoiding interference from the head unit to stop wireless charging or change a first frequency band to a second frequency band, and receiving a second signal from the head unit to resume the wireless charging or change to the first frequency band.