Method and device for slot generation in wireless power transmission system

The present disclosure provides a method for transmitting wireless power, performed by a wireless power transmitter, in a wireless power transmission system, and a device using same, the method comprising: entering a power transmission phase associated with transmitting the wireless power to a wireless power receiver; generating a slot in the power transmission phase; and performing foreign object detection on the slot, wherein the wireless power transmitter transmits the wireless power to the wireless power receiver on the basis of a first operating frequency before generating the slot, the wireless power transmitter resumes transmitting the wireless power on the basis of a second operating frequency after the slot is ended, and the second operating frequency is a higher frequency than the first operating frequency.