A wireless charging method performed by a wireless power receiving apparatus for a vehicle includes: producing a resonance between a primary pad located outside of the vehicle and a secondary pad installed in the vehicle based on an initial switching frequency; and tuning a switching frequency of a direct current (DC) to DC (DC-to-DC) converter within a range determined based on the initial switching frequency, according to an output voltage outputted based on a resonance of the secondary pad which is caused by the primary pad.